SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)	12 Months Ended
Dec. 31, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation Delta Air Lines, Inc., a Delaware corporation, provides scheduled air transportation for passengers and cargo throughout the United States ("U.S.") and around the world. Our Consolidated Financial Statements include the accounts of Delta Air Lines, Inc. and our consolidated subsidiaries and have been prepared in accordance with generally accepted accounting principles in the U.S. ("GAAP"). We are not the primary beneficiary of, nor do we have a controlling financial interest in, any variable interest entity. Accordingly, we have not consolidated any variable interest entity. We have marketing alliances with other airlines to enhance our access to domestic and international markets. These arrangements may include codesharing, reciprocal loyalty program benefits, shared or reciprocal access to passenger lounges, joint promotions, common use of airport gates and ticket counters, office co-location and other marketing agreements. We have received antitrust immunity for certain marketing arrangements, which enables us to offer a more integrated route network and develop common sales, marketing and discount programs for customers. Some of our marketing arrangements provide for the sharing of revenues and expenses. Revenues and expenses associated with the flights we operate under collaborative arrangements are presented on a gross basis in the applicable line items on our Consolidated Statements of Operations ("income statement"). We have reclassified certain prior period amounts to conform to the current period presentation. Unless otherwise noted, all amounts disclosed are stated before consideration of income taxes.
Use of Estimates	Use of Estimates We are required to make estimates and assumptions when preparing our Consolidated Financial Statements in accordance with GAAP. These estimates and assumptions affect the amounts reported in our Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates.
Recent Accounting Standards	Recent Accounting Standards Recently Adopted Standards In November 2023, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2023-07, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures." This standard requires disclosure of significant segment expenses and other segment items by reportable segment. We adopted this standard effective January 1, 2024. See Note 14, "Segments," for further information regarding our segment reporting. Standards Effective in Future Years Income Taxes. In December 2023, the FASB issued ASU No. 2023-09, "Income Taxes (Topic 740): Improvements to Income Tax Disclosures." This standard enhances disclosures related to income taxes, including the rate reconciliation and information on income taxes paid. This ASU is effective beginning January 1, 2025. Upon adoption of this ASU we expect to include certain additional disclosures in the effective income tax rate reconciliation in the footnotes to our Consolidated Financial Statements. Disaggregation of Income Statement Expenses. In November 2024, the FASB issued ASU No. 2024-03, "Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40)." This standard requires disclosure of specific information about costs and expenses and becomes effective January 1, 2027. We are assessing the impact of this ASU and, upon adoption, may be required to include certain additional disclosures in the footnotes to our Consolidated Financial Statements.
Cash and Cash Equivalents	Short-term, highly liquid investments with maturities of three months or less when purchased are classified as cash and cash equivalents.
Short-Term and Long-Term Investments	Investments with maturities of greater than three months, but not in excess of one year, when purchased were classified as short-term investments and stated at fair value. Investments with maturities beyond one year when purchased may be classified as short-term investments if they are expected to be available to support our short-term liquidity needs. Short-Term Investments. The fair values of our short-term investments were based on a market approach using industry standard valuation techniques that incorporate observable inputs such as quoted market prices, interest rates, benchmark curves, credit ratings of the security and other observable information. Long-Term Investments and Related. Our long-term investments measured at fair value primarily consist of equity investments, which are valued based on market prices or other observable transactions and inputs, and are recorded in equity investments on our balance sheets. Our equity investments in private companies are classified as Level 3 in the fair value hierarchy as their equity is not traded on a public exchange and our valuations incorporate certain unobservable inputs, including non-public equity issuances. Fair value measurement using unobservable inputs is inherently uncertain, and a change in significant inputs could result in different fair values. During the year ended December 31, 2024 there were no material gains or losses related to investments classified as Level 3 as a result of fair value adjustments. See Note 4, "Investments," for further information on our long-term investments.
Inventories	Inventories Fuel. As part of our strategy to mitigate the cost of the refining margin reflected in the price of jet fuel, our wholly owned subsidiary, Monroe Energy, LLC ("Monroe"), operates the Trainer oil refinery. Refined products (finished goods) and feedstock and blendstock inventories (work-in-process) are carried at the lower of cost and net realizable value. We use jet fuel in our airline operations that is produced by the refinery, procured through the exchanges with third parties of gasoline, diesel and other refined products ("non-jet fuel products") the refinery produces and purchased directly from third parties. Cost is determined using the first-in, first-out method. Costs include the raw material consumed plus direct manufacturing costs (such as labor, utilities and supplies) as incurred and an applicable portion of manufacturing overhead. Expendables Parts and Supplies. Inventories of expendable parts related to flight equipment, which cannot be economically repaired, reconditioned or reused after removal from the aircraft, are carried at moving average cost and charged to aircraft maintenance materials and outside repairs as consumed. An allowance for obsolescence is provided over the remaining useful life of the related fleet. We also provide allowances for parts identified as excess or obsolete to reduce the carrying costs to the lower of cost or net realizable value. These parts are estimated to have residual value of 5% of the original cost.
Accounting for Refinery Related Buy/Sell Agreements	Accounting for Refinery Related Buy/Sell Agreements To the extent that we receive jet fuel for non-jet fuel products exchanged under buy/sell agreements, we account for these transactions as nonmonetary exchanges. We have recorded these nonmonetary exchanges at the carrying amount of the non-jet fuel products transferred within aircraft fuel and related taxes on the income statement.
Derivatives and Fuel Hedge Contracts	Derivatives Changes in fuel prices, interest rates and foreign currency exchange rates impact our results of operations. In an effort to manage our exposure to these risks, we may enter into derivative contracts and adjust our derivative portfolio as market conditions change. Fuel Hedge Contracts. A portion of our derivative contracts may be negotiated over-the-counter with counterparties without going through a public exchange. Accordingly, our fair value assessments give consideration to the risk of counterparty default (as well as our own credit risk). Such contracts would be classified as Level 2 within the fair value hierarchy. The remainder of our hedge contracts may be comprised of futures contracts, which are traded on a public exchange. These contracts would be classified within Level 1 of the fair value hierarchy. Our derivative contracts to hedge the financial risk from changing fuel prices are related to Monroe’s inventory. Our fuel hedge portfolio may consist of a combination of options, swaps or futures. Option and swap contracts are valued under income approaches using option pricing models and discounted cash flow models, respectively, based on data either readily observable in public markets, derived from public markets or provided by counterparties who regularly trade in public markets. Futures contracts and options on futures contracts are traded on a public exchange and valued based on quoted market prices
Long-Lived Assets	Long-Lived Assets Our long-lived lived assets include property and equipment, net and operating lease right-of-use ("ROU") assets on our balance sheets. Our tangible assets consist primarily of flight equipment, which is mobile across geographic markets. Accordingly, assets are not allocated to specific geographic regions. We record property and equipment at cost and depreciate or amortize these assets on a straight-line basis to their estimated residual values over their estimated useful lives. The estimated useful life for leasehold improvements is the shorter of lease term or estimated useful life.We capitalize certain internal and external costs incurred to develop and implement software and amortize those costs over an estimated useful life of three to fifteen years.
Impairment of Long-Lived Assets	We review flight equipment, ROU assets and other long-lived assets used in operations for impairment losses when events and circumstances indicate the assets may be impaired. Factors which could be indicators of impairment include, but are not limited to (1) a decision to permanently remove flight equipment or other long-lived assets from operations, (2) significant changes in the estimated useful life, (3) significant changes in projected cash flows, (4) permanent and significant declines in fleet fair values and (5) changes to the regulatory environment. For long-lived assets held for sale, we discontinue depreciation and record impairment losses when the carrying amount of these assets is greater than the fair value less the cost to sell. To determine whether impairments exist for aircraft used in operations, we group assets at the fleet type level or at the contract level for aircraft operated by third-party regional carriers (i.e., the lowest level for which there are identifiable cash flows) and then estimate future cash flows based on projections of capacity, passenger mile yield, fuel and labor costs and other relevant factors. If an asset group is impaired, the impairment loss recognized is the amount by which the asset group's carrying amount exceeds its estimated fair value. We estimate aircraft fair values using published sources, appraisals and bids received from third parties, as available.
Fuel Card Obligation	Fuel Card Obligation We have a purchasing card with American Express for the purpose of buying jet fuel and crude oil.
Manufacturers' Credits	Manufacturers' Credits We periodically receive credits in connection with the acquisition of aircraft and engines or in connection with delivery delays or manufacturing defects. These credits are deferred until the aircraft and engines are delivered, and then applied as a reduction to the cost of the related equipment.
Maintenance Costs	Maintenance Costs We record maintenance costs related to our mainline and regional fleets in aircraft maintenance materials and outside repairs and regional carrier expense, respectively. Maintenance costs are expensed as incurred, except for costs incurred under power-by-the-hour contracts, which are expensed based on actual hours flown. Power-by-the-hour contracts transfer certain risk to third-party service providers and fix the amount we pay per flight hour or per flight cycle to the service provider in exchange for maintenance and repairs under a predefined maintenance program. Modifications that enhance the operating performance or extend the useful lives of airframes or engines are capitalized and amortized over the remaining estimated useful life of the asset or the remaining lease term, whichever is shorter.
Advertising Costs	Advertising Costs We expense advertising costs in passenger commissions and other selling expenses in the year the advertising first takes place.
Commissions and Merchant Fees	Commissions and Merchant Fees Passenger sales commissions and merchant fees are recognized in passenger commissions and other selling expenses when the related revenue is recognized.
Cash Equivalents and Restricted Cash Equivalents	Cash Equivalents and Restricted Cash Equivalents. Cash equivalents generally consist of money market funds. Restricted cash equivalents are recorded in other noncurrent assets and prepaid expenses and other on our balance sheets and generally consist of money market funds, time deposits, commercial paper and negotiable certificates of deposit, which primarily relate to proceeds from debt issued to finance, among other things, a portion of the construction costs for our new terminal facilities at New York's LaGuardia Airport as well as certain self-insurance obligations and airport commitments. The fair value of these cash equivalents is based on a market approach using prices generated by market transactions involving identical or comparable assets.
Goodwill and Indefinite-Lived Intangible Assets	Goodwill and Indefinite-Lived Intangible Assets Our goodwill and identifiable intangible assets relate to the airline segment. We apply a fair value-based impairment test to the carrying value of goodwill and indefinite-lived intangible assets on an annual basis (as of October 1) and, if certain events or circumstances indicate that an impairment loss may have been incurred, on an interim basis. We assess the value of our goodwill and indefinite-lived assets under either a qualitative or quantitative approach. Under a qualitative approach, we consider various market factors, including certain of the key assumptions listed below. We analyze these factors to determine if events and circumstances have affected the fair value of goodwill and indefinite-lived intangible assets. If we determine that it is more likely than not that the asset may be impaired, we use the quantitative approach to assess the asset's fair value and the amount of the impairment. Under a quantitative approach, we calculate the fair value of the asset incorporating the key assumptions listed below into our calculation. We value goodwill and indefinite-lived intangible assets primarily using market and income approach valuation techniques. These measurements include the following key assumptions (1) forecasted revenues, expenses and cash flows, (2) current discount rates, (3) observable market transactions and (4) anticipated changes to the regulatory environment (e.g., changes in slot access and/or availability, additional Open Skies agreements or changes to antitrust approvals). These assumptions are consistent with those that hypothetical market participants would use. Because we are required to make estimates and assumptions when evaluating goodwill and indefinite-lived intangible assets for impairment, actual transaction amounts may differ materially from these estimates. We recognize an impairment charge if the asset's carrying value exceeds its estimated fair value. Changes in certain events and circumstances could result in impairment or a change from indefinite-lived to definite-lived. Factors which could cause impairment include, but are not limited to (1) negative trends in our market capitalization, (2) reduced profitability resulting from lower passenger mile yields or higher input costs, (3) lower passenger demand as a result of weakened U.S. and global economies or other factors, (4) prolonged interruption to our operations, (5) changes to the regulatory environment, (6) operational or performance changes by other airlines and (7) strategic changes to our operations leading to diminished utilization of the intangible assets. Identifiable Intangible Assets. Indefinite-lived assets are not amortized and consist of routes, slots, the Delta tradename and assets related to alliances and collaborative arrangements. Definite-lived intangible assets consist primarily of marketing and maintenance service agreements and are amortized on a straight-line basis or under the undiscounted cash flows method over the estimated economic life of the respective agreements. Costs incurred to renew or extend the term of an intangible asset are expensed as incurred.

SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES (Policies)

12 Months Ended

Dec. 31, 2024

Delta Air Lines, Inc., a Delaware corporation, provides scheduled air transportation for passengers and cargo throughout the United States ("U.S.") and around the world. Our Consolidated Financial Statements include the accounts of Delta Air Lines, Inc. and our consolidated subsidiaries and have been prepared in accordance with generally accepted accounting principles in the U.S. ("GAAP"). We are not the primary beneficiary of, nor do we have a controlling financial interest in, any variable interest entity. Accordingly, we have not consolidated any variable interest entity.

We have marketing alliances with other airlines to enhance our access to domestic and international markets. These arrangements may include codesharing, reciprocal loyalty program benefits, shared or reciprocal access to passenger lounges, joint promotions, common use of airport gates and ticket counters, office co-location and other marketing agreements. We have received antitrust immunity for certain marketing arrangements, which enables us to offer a more integrated route network and develop common sales, marketing and discount programs for customers. Some of our marketing arrangements provide for the sharing of revenues and expenses. Revenues and expenses associated with the flights we operate under collaborative arrangements are presented on a gross basis in the applicable line items on our Consolidated Statements of Operations ("income statement").

We have reclassified certain prior period amounts to conform to the current period presentation. Unless otherwise noted, all amounts disclosed are stated before consideration of income taxes.

Use of Estimates

We are required to make estimates and assumptions when preparing our Consolidated Financial Statements in accordance with GAAP. These estimates and assumptions affect the amounts reported in our Consolidated Financial Statements and the accompanying notes. Actual results could differ materially from those estimates.

Recent Accounting Standards

Recently Adopted Standards

In November 2023, the Financial Accounting Standards Board ("FASB") issued Accounting Standards Update ("ASU") No. 2023-07, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures." This standard requires disclosure of significant segment expenses and other segment items by reportable segment. We adopted this standard effective January 1, 2024. See Note 14, "Segments," for further information regarding our segment reporting.

Standards Effective in Future Years

Income Taxes. In December 2023, the FASB issued ASU No. 2023-09, "Income Taxes (Topic 740): Improvements to Income Tax Disclosures." This standard enhances disclosures related to income taxes, including the rate reconciliation and information on income taxes paid. This ASU is effective beginning January 1, 2025. Upon adoption of this ASU we expect to include certain additional disclosures in the effective income tax rate reconciliation in the footnotes to our Consolidated Financial Statements.

Disaggregation of Income Statement Expenses. In November 2024, the FASB issued ASU No. 2024-03, "Income Statement - Reporting Comprehensive Income - Expense Disaggregation Disclosures (Subtopic 220-40)." This standard requires disclosure of specific information about costs and expenses and becomes effective January 1, 2027. We are assessing the impact of this ASU and, upon adoption, may be required to include certain additional disclosures in the footnotes to our Consolidated Financial Statements.

Cash and Cash Equivalents

Short-term, highly liquid investments with maturities of three months or less when purchased are classified as cash and cash equivalents.

Short-Term and Long-Term Investments

Investments with maturities of greater than three months, but not in excess of one year, when purchased were classified as short-term investments and stated at fair value. Investments with maturities beyond one year when purchased may be classified as short-term investments if they are expected to be available to support our short-term liquidity needs.

Short-Term Investments. The fair values of our short-term investments were based on a market approach using industry standard valuation techniques that incorporate observable inputs such as quoted market prices, interest rates, benchmark curves, credit ratings of the security and other observable information.

Long-Term Investments and Related. Our long-term investments measured at fair value primarily consist of equity investments, which are valued based on market prices or other observable transactions and inputs, and are recorded in equity investments on our balance sheets. Our equity investments in private companies are classified as Level 3 in the fair value hierarchy as their equity is not traded on a public exchange and our valuations incorporate certain unobservable inputs, including non-public equity issuances. Fair value measurement using unobservable inputs is inherently uncertain, and a change in significant inputs could result in different fair values. During the year ended December 31, 2024 there were no material gains or losses related to investments classified as Level 3 as a result of fair value adjustments. See Note 4, "Investments," for further information on our long-term investments.

Inventories

Fuel. As part of our strategy to mitigate the cost of the refining margin reflected in the price of jet fuel, our wholly owned subsidiary, Monroe Energy, LLC ("Monroe"), operates the Trainer oil refinery. Refined products (finished goods) and feedstock and blendstock inventories (work-in-process) are carried at the lower of cost and net realizable value. We use jet fuel in our airline operations that is produced by the refinery, procured through the exchanges with third parties of gasoline, diesel and other refined products ("non-jet fuel products") the refinery produces and purchased directly from third parties. Cost is determined using the first-in, first-out method. Costs include the raw material consumed plus direct manufacturing costs (such as labor, utilities and supplies) as incurred and an applicable portion of manufacturing overhead.

Expendables Parts and Supplies. Inventories of expendable parts related to flight equipment, which cannot be economically repaired, reconditioned or reused after removal from the aircraft, are carried at moving average cost and charged to aircraft maintenance materials and outside repairs as consumed. An allowance for obsolescence is provided over the remaining useful life of the related fleet. We also provide allowances for parts identified as excess or obsolete to reduce the carrying costs to the lower of cost or net realizable value. These parts are estimated to have residual value of 5% of the original cost.

Accounting for Refinery Related Buy/Sell Agreements

To the extent that we receive jet fuel for non-jet fuel products exchanged under buy/sell agreements, we account for these transactions as nonmonetary exchanges. We have recorded these nonmonetary exchanges at the carrying amount of the non-jet fuel products transferred within aircraft fuel and related taxes on the income statement.

Derivatives and Fuel Hedge Contracts

Derivatives

Changes in fuel prices, interest rates and foreign currency exchange rates impact our results of operations. In an effort to manage our exposure to these risks, we may enter into derivative contracts and adjust our derivative portfolio as market conditions change. Fuel Hedge Contracts. A portion of our derivative contracts may be negotiated over-the-counter with counterparties without going through a public exchange. Accordingly, our fair value assessments give consideration to the risk of counterparty default (as well as our own credit risk). Such contracts would be classified as Level 2 within the fair value hierarchy. The remainder of our hedge contracts may be comprised of futures contracts, which are traded on a public exchange. These contracts would be classified within Level 1 of the fair value hierarchy. Our derivative contracts to hedge the financial risk from changing fuel prices are related to Monroe’s inventory. Our fuel hedge portfolio may consist of a combination of options, swaps or futures. Option and swap contracts are valued under income approaches using option pricing models and discounted cash flow models, respectively, based on data either readily observable in public markets, derived from public markets or provided by counterparties who regularly trade in public markets. Futures contracts and options on futures contracts are traded on a public exchange and valued based on quoted market prices

Long-Lived Assets

Our long-lived lived assets include property and equipment, net and operating lease right-of-use ("ROU") assets on our balance sheets. Our tangible assets consist primarily of flight equipment, which is mobile across geographic markets. Accordingly, assets are not allocated to specific geographic regions. We record property and equipment at cost and depreciate or amortize these assets on a straight-line basis to their estimated residual values over their estimated useful lives. The estimated useful life for leasehold improvements is the shorter of lease term or estimated useful life.We capitalize certain internal and external costs incurred to develop and implement software and amortize those costs over an estimated useful life of three to fifteen years.

Impairment of Long-Lived Assets

We review flight equipment, ROU assets and other long-lived assets used in operations for impairment losses when events and circumstances indicate the assets may be impaired. Factors which could be indicators of impairment include, but are not limited to (1) a decision to permanently remove flight equipment or other long-lived assets from operations, (2) significant changes in the estimated useful life, (3) significant changes in projected cash flows, (4) permanent and significant declines in fleet fair values and (5) changes to the regulatory environment. For long-lived assets held for sale, we discontinue depreciation and record impairment losses when the carrying amount of these assets is greater than the fair value less the cost to sell.

To determine whether impairments exist for aircraft used in operations, we group assets at the fleet type level or at the contract level for aircraft operated by third-party regional carriers (i.e., the lowest level for which there are identifiable cash flows) and then estimate future cash flows based on projections of capacity, passenger mile yield, fuel and labor costs and other relevant factors. If an asset group is impaired, the impairment loss recognized is the amount by which the asset group's carrying amount exceeds its estimated fair value. We estimate aircraft fair values using published sources, appraisals and bids received from third parties, as available.

Fuel Card Obligation

We have a purchasing card with American Express for the purpose of buying jet fuel and crude oil.

Manufacturers' Credits

We periodically receive credits in connection with the acquisition of aircraft and engines or in connection with delivery delays or manufacturing defects. These credits are deferred until the aircraft and engines are delivered, and then applied as a reduction to the cost of the related equipment.

Maintenance Costs

We record maintenance costs related to our mainline and regional fleets in aircraft maintenance materials and outside repairs and regional carrier expense, respectively. Maintenance costs are expensed as incurred, except for costs incurred under power-by-the-hour contracts, which are expensed based on actual hours flown. Power-by-the-hour contracts transfer certain risk to third-party service providers and fix the amount we pay per flight hour or per flight cycle to the service provider in exchange for maintenance and repairs under a predefined maintenance program. Modifications that enhance the operating performance or extend the useful lives of airframes or engines are capitalized and amortized over the remaining estimated useful life of the asset or the remaining lease term, whichever is shorter.

Advertising Costs

We expense advertising costs in passenger commissions and other selling expenses in the year the advertising first takes place.

Commissions and Merchant Fees

Passenger sales commissions and merchant fees are recognized in passenger commissions and other selling expenses when the related revenue is recognized.

Cash Equivalents and Restricted Cash Equivalents

Cash Equivalents and Restricted Cash Equivalents. Cash equivalents generally consist of money market funds. Restricted cash equivalents are recorded in other noncurrent assets and prepaid expenses and other on our balance sheets and generally consist of money market funds, time deposits, commercial paper and negotiable certificates of deposit, which primarily relate to proceeds from debt issued to finance, among other things, a portion of the construction costs for our new terminal facilities at New York's LaGuardia Airport as well as certain self-insurance obligations and airport commitments. The fair value of these cash equivalents is based on a market approach using prices generated by market transactions involving identical or comparable assets.

Goodwill and Indefinite-Lived Intangible Assets

Our goodwill and identifiable intangible assets relate to the airline segment. We apply a fair value-based impairment test to the carrying value of goodwill and indefinite-lived intangible assets on an annual basis (as of October 1) and, if certain events or circumstances indicate that an impairment loss may have been incurred, on an interim basis. We assess the value of our goodwill and indefinite-lived assets under either a qualitative or quantitative approach. Under a qualitative approach, we consider various market factors, including certain of the key assumptions listed below. We analyze these factors to determine if events and circumstances have affected the fair value of goodwill and indefinite-lived intangible assets. If we determine that it is more likely than not that the asset may be impaired, we use the quantitative approach to assess the asset's fair value and the amount of the impairment. Under a quantitative approach, we calculate the fair value of the asset incorporating the key assumptions listed below into our calculation.

We value goodwill and indefinite-lived intangible assets primarily using market and income approach valuation techniques. These measurements include the following key assumptions (1) forecasted revenues, expenses and cash flows, (2) current discount rates, (3) observable market transactions and (4) anticipated changes to the regulatory environment (e.g., changes in slot access and/or availability, additional Open Skies agreements or changes to antitrust approvals). These assumptions are consistent with those that hypothetical market participants would use. Because we are required to make estimates and assumptions when evaluating goodwill and indefinite-lived intangible assets for impairment, actual transaction amounts may differ materially from these estimates. We recognize an impairment charge if the asset's carrying value exceeds its estimated fair value.

Changes in certain events and circumstances could result in impairment or a change from indefinite-lived to definite-lived. Factors which could cause impairment include, but are not limited to (1) negative trends in our market capitalization, (2) reduced profitability resulting from lower passenger mile yields or higher input costs, (3) lower passenger demand as a result of weakened U.S. and global economies or other factors, (4) prolonged interruption to our operations, (5) changes to the regulatory environment, (6) operational or performance changes by other airlines and (7) strategic changes to our operations leading to diminished utilization of the intangible assets.

Identifiable Intangible Assets. Indefinite-lived assets are not amortized and consist of routes, slots, the Delta tradename and assets related to alliances and collaborative arrangements. Definite-lived intangible assets consist primarily of marketing and maintenance service agreements and are amortized on a straight-line basis or under the undiscounted cash flows method over the estimated economic life of the respective agreements. Costs incurred to renew or extend the term of an intangible asset are expensed as incurred.