We finance apartment communities in our portfolio primarily using property-level, non-recourse, long-dated, fixed-rate, amortizing debt. The following table summarizes non-recourse property debt as of December 31, 2020 and 2019 (dollars in thousands):

				Outstanding Balance as of December 31,
	Latest Maturity Date	Interest Rate Range	Weighted-Average Interest Rate	2020			2019
Fixed-rate property debt	January 1, 2055	2.42% to 6.01%	3.55%	$	3,631,588		$	3,740,648
Variable-rate property debt	July 13, 2033	1.09% to 1.15%	1.12%		14,505			14,505
Total non-recourse property debt					3,646,093			3,755,153
Debt issuance costs, net of accumulated amortization					(17,857	)		(17,348	)
Non-recourse property debt, net				$	3,628,236		$	3,737,805

Principal and interest on fixed-rate debt are generally payable monthly or in monthly interest-only payments with balloon payments due at maturity. As of December 31, 2020, our fixed-rate property debt was secured by 57 apartment communities that had an aggregate net book value of $3.7 billion.

Principal and interest on variable-rate debt are generally payable in semi-annual installments with balloon payments due at maturity. As of December 31, 2020, our variable-rate property debt was secured by three apartment communities that had an aggregate net book value of $14.5 million.

These non-recourse property debt instruments contain covenants common to the type of borrowing, and as of December 31, 2020, we were in compliance with all such covenants.

As of December 31, 2020, the scheduled principal amortization and maturity payments for the non-recourse property debt were as follows (in thousands):

	Amortization		Maturities		Total
2021	$	67,922	$	35,848	$	103,770
2022		68,836		201,264		270,100
2023		63,939		160,670		224,609
2024		63,112		154,685		217,797
2025		57,883		355,013		412,896
Thereafter		322,412		2,094,509		2,416,921
Total	$	644,104	$	3,001,989	$	3,646,093

On December 15, 2020, in connection with the Separation, we decreased the maximum borrowing capacity of our revolving credit facility from $800.0 million to $600.0 million, reflecting reduced borrowing needs with the elimination of redevelopment and development projects. In addition to the revolving credit facility, our credit agreement also includes a $350.0 million term loan, which was secured on April 20, 2020. The loan matures on April 20, 2021, includes a one-year extension option, and currently bears interest at a 30-day LIBOR plus 1.60%, with a 50 basis point LIBOR floor. Proceeds from the loan were used primarily to repay borrowings on our revolving credit facility.

Borrowings against our revolving credit facility bear interest at a rate set forth on a pricing grid, which rate varies based on our credit rating as assigned by specified rating agencies (LIBOR plus 1.00%, or, at our option, a base rate plus 0.0% as of December 31, 2020). Swing line loans will bear interest at the base rate plus the applicable margin. The revolving credit agreement matures on January 22, 2022. As of December 31, 2020 and 2019, we had $265.6 million and $275.0 million, respectively, of outstanding borrowings under our revolving credit facility. The interest rate on our outstanding borrowings was 1.46% and 3.00% as of December 31, 2020 and 2019, respectively. As of December 31, 2020, after outstanding borrowings and $23.7 million of undrawn letters of credit backed by the revolving credit facility, our available borrowing capacity was $310.7 million.

We have agreed to maintain a fixed charge coverage ratio of 1.40x, as well as other covenants customary for similar revolving credit arrangements. We expect to remain in compliance with these covenants. Our credit agreement provides that we may make distributions to our investors during any four consecutive quarters in an aggregate amount that does not exceed the greater of 95% of our funds from operations, as defined by NAREIT, for such period, subject to certain non-cash adjustments, or such amount as may be necessary to maintain AIR’s REIT status.