Unbilled receivables decreased from $9,043 at December 31, 2019 to $7,995 at December 31, 2020, primarily driven by an increase in billings at BDS and BGS, as well as an increase in allowances for expected credit losses at BGS.

Advances and progress billings decreased from $51,551 at December 31, 2019 to $50,488 at December 31, 2020, primarily driven by revenue recognized in excess of advances on orders received and return of BCA customer advances, partially offset by advances on orders received at BCA, BDS, and BGS.

Revenues recognized for the years ended December 31, 2020 and 2019 from amounts recorded as Advances and progress billings at the beginning of each year were $10,360 and $16,778.

Certain commercial airplane customers are experiencing liquidity issues and seeking additional capital. Should these customers fail to address their liquidity issues, accounts receivable, unbilled receivables and certain inventory could become impaired. In addition we would have to remove contracts related to these customers from backlog and remarket any undelivered aircraft.

The following table summarizes our contract assets under long-term contracts that were unbillable or related to outstanding claims as of December 31:


	Unbilled		Claims
	2020	2019	2020	2019
Current	$5,628	$6,931		$9
Expected to be collected after one year	2,496	2,112	18	14
Less valuation allowance(1)	(129)
Total	$7,995	$9,043	$18	$23

Unbilled receivables related to commercial customer incentives expected to be collected after one year were $178 and $211 at December 31, 2020 and 2019. Unbilled receivables related to claims are items that we believe are earned, but are subject to uncertainty concerning their determination or ultimate realization.