Certain significant amounts included in the Company's consolidated balance sheets as of September 30, 2022 and 2021, consisted of the following (in thousands):

	September 30,			September 30,
	2022			2021
Expendable parts and supplies, net:
Expendable parts and supplies	$	31,913		$	29,297
Less: obsolescence and other		(5,198	)		(4,830	)
	$	26,715		$	24,467
Prepaid expenses and other current assets:
Prepaid aviation insurance	$	2,618		$	2,171
Prepaid vendors		1,310		893
Prepaid other insurance		1,268			1,323
Lease Incentives		352			1,445
Other		1,068			1,053
	$	6,616		$	6,885
Property and equipment, net:
Aircraft and other flight equipment substantially pledged	$	1,260,143		$	1,611,544
Other equipment		5,577			4,934
Leasehold improvements		2,776			2,776
Vehicles		992			1,184
Building		777			699
Furniture and fixtures		298			300
Total property and equipment		1,270,563			1,621,437
Less: accumulated depreciation		(405,309	)		(469,546	)
	$	865,254		$	1,151,891
Other assets:
Investments in equity securities	$	15,178		$	25,149
Lease incentives		1,097			10,957
Other		15			15
	$	16,290		$	36,121
Other accrued expenses:
Accrued property taxes	$	5,866		$	8,783
Accrued interest		2,882			2,565
Accrued vacation		4,746			5,936
Accrued lodging		3,795			3,380
Accrued maintenance		1,453			1,580
Accrued liability on government payroll program		2,967			2,775
Accrued simulator costs		1,045		457
Accrued employee benefits		1,679		981
Accrued fleet operating expense		1,606		786
Short term lease incentive liability	97				3,318
Other		2,864			3,096
	$	29,000		$	33,657
Other noncurrent liabilities:
Warrant liabilities	$	25,225		$	21,964
Lease incentive obligations		1,050			6,358
Long term employee benefits		1,123			1,447
Long term liability on government payroll program	—				2,775
Other		1,821			2,047
	$	29,219		$	34,591

The Company monitors for any indicators of impairment of the long-lived fixed assets. When certain conditions or changes in the economic situation exist, the assets may be impaired and the carrying amount of the assets exceed its fair value. The assets are then tested for recoverability of carrying amount. The Company records impairment charges on long-lived assets used in operations when events and circumstances indicate that the assets may be impaired, the undiscounted net cash flows estimated to be generated by those assets are less than the carrying amount of those assets, and the net book value of the assets exceeds their estimated fair value.

We group assets at the capacity purchase agreement, flight services agreement, and fleet-type level (i.e., the lowest level for which there are identifiable cash flows). If impairment indicators exist with respect to any of the asset groups, we estimate future cash flows based on projections of capacity purchase or flight services agreement, block hours, maintenance events, labor costs and other relevant factors.

Due to the impacts of the pilot shortage and the pilot wage increase, the Company assessed whether any impairment of its long-lived assets existed for all asset groups during the quarter ended September 30, 2022. The Company has determined that impairment charges were deemed necessary only for the asset group associated with the CRJ-900 fleet operating under the American CPA because the future cash flows from the operation of other asset groups through the respective retirement dates exceeded the carrying value. The asset group associated with the CRJ-900 fleet includes owned aircraft, leased aircraft, intangible assets of customer relationship, and other relevant long-lived assets. The fair values of assets within the CRJ-900 fleet were calculated using Level 3 fair value inputs based primarily upon recent market transactions, appraisals, and third-party bids, which were corroborated with published pricing guides and our assessment of existing market conditions based on industry knowledge. For the year ended September 30, 2022, the Company recognized a total impairment loss of $109.7 million related to the asset group associate with the CRJ-900 fleet, of which $92.6 million was related to property and equipment, $15.2 million was related to operating lease right-of-use assets, and $1.9 million was related to intangible asset of customer relationship. These impairment charges were recorded in asset impairment on our consolidated statements of operations and comprehensive (loss) income. The Company did not record any impairment losses related to its long-lived assets during the years ended September 30, 2021 and 2020.

The Company’s assumptions about future conditions important to its assessment of potential impairment of its long-lived assets, including the impact of the COVID-19 pandemic to its business, are subject to uncertainty, and the Company will continue to monitor these conditions in future periods as new information becomes available, and will update its analyses accordingly.

Depreciation expense on property and equipment totaled $80.5 million, $81.2 million and $80.8 million for the years ended September 30, 2022, 2021, and 2020, respectively.

In connection with a negotiated forward purchase contract for electrically-powered vertical takeoff and landing aircraft (“eVTOL aircraft”) executed in February 2021, we obtained equity warrant assets giving us the right to acquire a number shares of common stock in Archer Aviation, Inc. (“Archer”), which at the time of our initial investment was a private, venture-backed company. As the initial investment in Archer did not have a readily determinable fair value, we accounted for this investment using the measurement alternative under ASC 321 and measured the investments at cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments from the same issuer. We estimated the initial equity warrant asset value to be $16.4 million based on publicly available information as of the grant date. In September 2021, the merger between Archer and a special purpose acquisition company (“SPAC”) was completed, resulting in a readily determinable fair value of our investments in Archer. Accordingly, gains and losses associated with changes in the fair value of our investments in Archer are measured in earnings, in accordance with ASC 321.

The initial grant date value of the warrants, $16.4 million, was recognized as a vendor credit liability within other noncurrent liabilities. The liability related to the warrant assets will be settled in the future, as a reduction of the acquisition date value of the eVTOL aircraft contemplated in the related aircraft purchase agreement.

In connection with closing of the merger between Archer and the SPAC described above, in September 2021, we purchased 500,000 Class A common shares in Archer for $5.0 million, and obtained an additional warrant to purchase shares of Archer with a total grant date value of $5.6 million. The initial value of the warrants was recognized as a vendor credit liability within other noncurrent liabilities, and will be settled in the future, as a reduction of the acquisition date value of the eVTOL aircraft contemplated in the related aircraft purchase agreement. Because these investments have readily

determinable fair values, gains and losses resulting from changes in fair value of the investments are reflected in earnings, in accordance with ASC 321. All of our vested warrants have been exercised into shares of Archer common stock.

Losses on our investments in Archer totaled $13.7 million and $6.8 million during the fiscal years ended September 30, 2022 and 2021, and are reflected in loss on investments, net in our Consolidated Statements of Operations and Comprehensive (Loss) Income.

The fair values of the Company’s investments in Archer are Level 1 within the fair value hierarchy as the values are determined using quoted prices for the equity securities.

In connection with a negotiated forward purchase contract for fully electric aircraft executed in July 2021, we obtained $5.0 million of preferred stock in Heart Aerospace Incorporated (“Heart”), a privately held company. Our investment in Heart does not have a readily determinable fair value, so we account for the investment using the measurement alternative under ASC 321 and measure the investment at initial cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments from the same issuer. We consider a range of factors when adjusting the fair value of these investments, including, but not limited to, the term and nature of the investment, local market conditions, values for comparable securities, current and projected operating performance, financing transactions subsequent to the acquisition of the investment, or other features that indicate a change to fair value is warranted. Any changes in fair value from the initial cost of the investment in preferred stock are recognized as increases or decreases on our balance sheet and as net gains or losses on investments in equity securities, in other income (expense), net. The initial investment in preferred stock was measured at cost of $5.0 million. There were no identical or similar transactions during the fiscal year ended September 30, 2022, and as such, no adjustments to the initial cost of the equity investment resulting from observable price changes have been recorded at September 30, 2022.

In connection with a negotiated forward purchase contract for hybrid-electric vertical takeoff and landing (“VTOL”) aircraft executed in February 2022, we obtained a warrant giving us the right to acquire a number of shares of common stock in the privately-held manufacturer of the VTOL aircraft. These investments do not have a readily determinable fair value, so we account for them using the measurement alternative under ASC 321 and measure the investments at cost less impairment, if any, plus or minus changes resulting from observable price changes in orderly transactions for identical or similar investments from the same issuer. We consider a range of factors when adjusting the fair value of these investments, including, but not limited to, the term and nature of the investment, local market conditions, values for comparable securities, current and projected operating performance, financing transactions subsequent to the acquisition of the investment or other features that indicate a discount to fair value is warranted. Any changes in fair value from the grant date value of the warrant assets will be recognized as increases or decreases to the investment on our balance sheet and as net gains or losses on investments equity securities. We estimated the initial warrant asset value to be $3.2 million based on prices of similar investments in the same issuer. The grant date value of the warrants, $3.2 million, was recognized as a vendor credit liability within other noncurrent liabilities. The liability related to the warrant assets will be settled in the future, as a reduction of the acquisition date value of the VTOL aircraft contemplated in the related forward purchase agreement.

Total net losses on our investments in equity securities totaled $13.7 million during the year ended September 30, 2022, respectively, and are reflected in loss on investments, net in our consolidated statements of operations and comprehensive (loss) income. As of September 30, 2022, the aggregate carrying amount of our investments in equity securities was $15.2 million, and the carrying amount of our investments without readily determinable fair values was $9.0 million.