Financing receivables and operating lease equipment, net consisted of the following at December 31:


	2023	2022
Financing receivables:
Investment in sales-type leases	$556	$804
Notes	102	385
Total financing receivables	658	1,189
Less allowance for losses on receivables	51	55
Financing receivables, net	607	1,134
Operating lease equipment, at cost, less accumulated depreciation of $70 and $76	352	470

Total	$959	$1,604

Financing arrangements typically range in terms from 1 to 12 years and may include options to extend or terminate. Certain leases include provisions to allow the lessee to purchase the underlying aircraft at a specified price. At December 31, 2023 and 2022, $44 and $405 were determined to be uncollectible financing receivables and placed on non-accrual status. The allowance for losses on receivables remained largely unchanged during the year ended December 31, 2023.


	2023	2022
Gross lease payments receivable	$697	$924
Unearned income	(162)	(206)
Net lease payments receivable	535	718
Unguaranteed residual assets	21	86
Total	$556	$804

Financing interest income received for the years ended December 31, 2023 and 2022 was $108 and $13.

Our financing receivable balances at December 31, 2023 by internal credit rating category and year of origination consisted of the following:


Rating categories	Current	2022	2021	2020	2019	Prior	Total
BBB						$13	$13
BB	$73	$32	$198	$103	$36	53	495
B					12	94	106
CCC			35			9	44


Total carrying value of financing receivables	$73	$32	$233	$103	$48	$169	$658

At December 31, 2023, our allowance for losses related to receivables with ratings of CCC, B, BB and BBB. We applied default rates that averaged 100.0%, 0.0%, 2.4% and 0.1%, respectively, to the exposure associated with those receivables.

The majority of our financing receivables and operating lease equipment portfolio is concentrated in the following aircraft models at December 31:


	2023	2022
717 Aircraft ($0 and $45 accounted for as operating leases)	$478	$563
747-8 Aircraft (Accounted for as sales-type leases)	129	394
737 Aircraft ($148 and $174 accounted for as operating leases)	156	186
777 Aircraft ($194 and $209 accounted for as operating leases)	194	209
MD-80 Aircraft (Accounted for as sales-type leases)		96
757 Aircraft (Accounted for as sales-type leases)		107
747-400 Aircraft (Accounted for as sales-type leases)	43	46

Impairment charges related to operating lease assets were $0, $7, and $31 for the years ended December 31, 2023, 2022 and 2021.

Lease income recorded in Sales of services on the Consolidated Statements of Operations for the years ended December 31, 2023, 2022 and 2021 included $55, $69, and $54 of interest income from

sales-type leases, and $60, $65, and $68 from operating lease payments. Profit at the commencement of sales-type leases was recorded in Sales of services for the years ended December 31, 2023, 2022 and 2021 in the amount of $32, $28, and $78.

As of December 31, 2023, undiscounted cash flows for notes receivable, sales-type and operating leases over the next five years and thereafter are as follows:


	Notes receivable	Sales-type leases	Operating leases
Year 1	$17	$149	$69
Year 2	9	102	61
Year 3	10	109	52
Year 4	11	127	47
Year 5	12	137	45
Thereafter	43	73	48
Total financing receipts	102	697	322
Less imputed interest		(162)
Estimated unguaranteed residual values		21
Total	$102	$556	$322