As of December 31, 2022, we leased 17 aircraft, airport facilities, office space, and other property and equipment under non-cancelable operating leases. The leases generally require us to pay all taxes, maintenance, insurance, and other operating expenses. Rental expense is recognized on a straight-line basis over the lease term, net of lessor rebates and other incentives. We expect that, in the normal course of business, such operating leases that expire will be renewed or replaced by other leases, or the property may be purchased rather than leased.

Aggregate rental expense under all operating aircraft, equipment and facility leases totaled approximately $6.9 million and $11.8 million for the three months ended December 31, 2022 and 2021, respectively.

The components of our operating lease costs were as follows (in thousands):


	Three Months Ended December 31,
	2022		2021
Operating lease costs	$	4,699	$	9,480
Variable and short-term lease costs		889		1,735
Interest expense on finance lease liabilities		274		100
Amortization expense of finance lease assets		1,046		533
Total lease costs	$	6,907	$	11,848

As of December 31, 2022, our operating leases have a remaining weighted average lease term of 6.0 years and our operating lease liabilities were measured using a weighted average discount rate of 4.8%.

Due to the impacts of the pilot shortage and the pilot wage increase, we evaluated all asset groups during the fiscal year ended September 30, 2022 and determined that only the asset group associated with the CRJ-900 fleet operating under the American CPA, discussed in Note 7, required impairment. As of the three months ended December 31, 2022, we determined zero further impairment is required within the asset group for the CRJ-900 fleet on our condensed consolidated statements of operations and comprehensive loss. Additionally, during the three months ended December 31, 2022, we recorded a zero impairment of certain operating lease ROU assets associated with the abandonment of a leased facility. The Company did not record any impairment losses related to its operating lease right-of-use assets during the three months ended December 31, 2021.

Historically, Mesa Airlines, as lessee, entered into the RASPRO Lease Facility, with RASPRO as lessor, for 15 of our CRJ-900 aircraft classified as operating leases. The obligations under the RASPRO Lease Facility are guaranteed by us, and basic rent is paid quarterly on each aircraft. During December 2022, the Company entered into an agreement with RASPRO Trust, reducing the buyout pricing on all 15 aircraft at lease termination by a total of $25 million. Under the terms of the new agreement, the Company reclassified these leases as finance leases.