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Fair Value Measurements - Measured on Recurring Basis (Details) - USD ($)
$ in Millions

Dec. 31, 2018

Dec. 31, 2017

Assets

Time Deposits

$ 25

Fuel derivatives:

Derivative Asset, Fair Value, Gross Asset

^[1]

138

$ 283

Fuel derivatives:

Derivative Liability, Fair Value, Gross Liability

^[1]

(14)

(57)

Quoted prices in active markets for identical assets (Level 1)

Assets

Time Deposits

0

Significant other observable inputs (Level 2)

Assets

Time Deposits

25

Significant unobservable inputs (Level 3)

Assets

Time Deposits

0

Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)

Assets

Treasury bills

1,582

1,491

Fuel derivatives:

Other available for sale securities

127

107

Assets, Fair Value Disclosure

3,101

2,731

Fuel derivatives:

Interest rate derivatives (see Note 10)

0

0

Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)

Assets

Treasury bills

0

0

Fuel derivatives:

Other available for sale securities

0

0

Assets, Fair Value Disclosure

715

649

Fuel derivatives:

Interest rate derivatives (see Note 10)

(14)

(22)

Total Liabilities

(22)

Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)

Assets

Treasury bills

0

0

Fuel derivatives:

Assets, Fair Value Disclosure

138

283

Fuel derivatives:

Interest rate derivatives (see Note 10)

0

0

Total Liabilities

(35)

Cash Equivalents | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)

Assets

Cash equivalents

^[2]

1,392

1,133

Cash Equivalents | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)

Assets

Cash equivalents

^[2]

0

0

Cash Equivalents | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)

Assets

Cash equivalents

^[2]

0

0

Commercial paper | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)

Assets

Cash equivalents

0

0

Commercial paper | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)

Assets

Cash equivalents

454

350

Commercial paper | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)

Assets

Cash equivalents

0

0

Certificates of deposit | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)

Assets

Cash equivalents

0

0

Certificates of deposit | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)

Assets

Cash equivalents

8

12

Certificates of deposit | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)

Assets

Cash equivalents

0

0

Certificates of deposit | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)

Assets

Investments

0

0

Certificates of deposit | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)

Assets

Investments

228

287

Certificates of deposit | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)

Assets

Investments

0

0

Options Held | Fair Value, Measurements, Recurring | Quoted prices in active markets for identical assets (Level 1)

Fuel derivatives:

Derivative Asset, Fair Value, Gross Asset

^[3]

0

0

Fuel derivatives:

Derivative Asset, Fair Value, Gross Liability

^[3]

0

Options Held | Fair Value, Measurements, Recurring | Significant other observable inputs (Level 2)

Fuel derivatives:

Derivative Asset, Fair Value, Gross Asset

^[3]

0

0

Fuel derivatives:

Derivative Asset, Fair Value, Gross Liability

^[3]

0

Options Held | Fair Value, Measurements, Recurring | Significant unobservable inputs (Level 3)

Fuel derivatives:

Derivative Asset, Fair Value, Gross Asset

^[3]

138

283

Fuel derivatives:

Derivative Asset, Fair Value, Gross Liability

^[3]

(35)

Period end date | Fair Value, Measurements, Recurring

Assets

Treasury bills

1,582

1,491

Fuel derivatives:

Other available for sale securities

127

107

Assets, Fair Value Disclosure

3,954

3,663

Fuel derivatives:

Interest rate derivatives (see Note 10)

(14)

(22)

Total Liabilities

(57)

Period end date | Cash Equivalents | Fair Value, Measurements, Recurring

Assets

Cash equivalents

^[2]

1,392

1,133

Period end date | Commercial paper | Fair Value, Measurements, Recurring

Assets

Cash equivalents

454

350

Period end date | Certificates of deposit | Fair Value, Measurements, Recurring

Assets

Cash equivalents

8

12

Period end date | Certificates of deposit | Fair Value, Measurements, Recurring

Assets

Investments

228

287

Period end date | Options Held | Fair Value, Measurements, Recurring

Fuel derivatives:

Derivative Asset, Fair Value, Gross Asset

^[3]

$ 138

283

Fuel derivatives:

Derivative Asset, Fair Value, Gross Liability

^[3]

$ (35)

[1]	Represents the position of each trade before consideration of offsetting positions with each counterparty and does not include the impact of cash collateral deposits provided to or received from counterparties. See discussion of credit risk and collateral following in this Note.
[2]	Cash equivalents are primarily composed of money market investments.
[3]	In the Consolidated Balance Sheet amounts are presented as an asset. See Note 10.

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