5. Debt Obligations

Debt obligations consisted of the following:


	As of December 31,
	2018		2017
	(in thousands)
Credit facility at a floating rate of interest of one-month LIBOR plus 2.0% at December 31, 2018, secured by engines. The facility has a committed amount of $890.0 million at December 31, 2018, which revolves until the maturity date of April 2021	$	427,000	$	491,000
WEST IV Series A 2018 term notes payable at a fixed rate of interest of 4.75%, maturing in September 2043, secured by engines		323,075		—
WEST IV Series B 2018 term notes payable at a fixed rate of interest of 5.44%, maturing in September 2043, secured by engines		46,154		—
WEST III Series A 2017 term notes payable at a fixed rate of interest of 4.69%, maturing in August 2042, secured by engines		274,205		289,295
WEST III Series B 2017 term notes payable at a fixed rate of interest of 6.36%, maturing in August 2042, secured by engines		39,212		41,370
WEST II Series A 2012 term notes payable at a fixed rate of interest of 5.50%, maturing in September 2037, secured by engines		237,847		259,022
Note payable at fixed interest rates ranging from 2.60% to 2.97%, maturing in July 2024, secured by a corporate aircraft		10,937		12,720
Note payable at a variable interest rate of one-month LIBOR plus 2.25%, matured in January 2018, secured by engines		—		10,336
		1,358,430		1,103,743
Less: unamortized debt issuance costs		(21,081)		(18,338)
Total debt obligations	$	1,337,349	$	1,085,405

One-month LIBOR was 2.50% and 1.57% as of December 31, 2018 and December 31, 2017, respectively.

Principal outstanding at December 31, 2018, is repayable as follows:


Year	(in thousands)
2019	$	55,380
2020		54,980
2021 (includes $427.0 million outstanding on revolving credit facility)		482,217
2022 (includes $173.8 million outstanding on WEST II Series A 2012 term notes)		207,733
2023		34,008
Thereafter		524,112
Total	$	1,358,430

Virtually all of the above debt requires ongoing compliance with the covenants of each financing, including debt/equity ratios, minimum tangible net worth and minimum interest coverage ratios, and other eligibility criteria including customer and geographic concentration restrictions. The Company also has certain negative financial covenants such as liens, advances, change in business, sales of assets, dividends and stock repurchases. These covenants are tested either monthly or quarterly and the Company was in full compliance with all financial covenant requirements at December 31, 2018.

At December 31, 2018, the Company had a revolving credit facility to finance the acquisition of equipment for lease as well as for general working capital purposes, with the amounts drawn under the facility not to exceed that which is allowed under the borrowing base as defined by the credit agreement. In April 2016, the Company entered into a Third Amended and Restated Credit Agreement which increased the revolving credit facility to $890.0 million from $700.0 million and extended the term to April 2021. This $890 million revolving credit facility has an accordion feature which would expand the entire credit facility up to $1 billion. As of December 31, 2018 and 2017, $463.0 million and $399.0 million were available under this facility, respectively. On a quarterly basis, the interest rate is adjusted based on the Company’s leverage ratio, as calculated under the terms of the revolving credit facility. Under the revolving credit facility, all subsidiaries except WEST II, WEST III, and WEST IV jointly and severally guarantee payment and performance of the terms of the loan agreement. The guarantee would be triggered by a default under the agreement.

At December 31, 2018, $369.2 million of WEST IV term notes were outstanding. At December 31, 2018 and 2017, $313.4 million and $330.7 million of WEST III term notes were outstanding, respectively. At December 31, 2018 and 2017, $237.8 million and $259.0 million of WEST II term notes were outstanding, respectively.

The assets of WEST II, WEST III and WEST IV are not available to satisfy the Company’s obligations other than the obligations specific to that WEST entity. WEST II, WEST III and WEST IV are consolidated for financial statement presentation purposes. WEST II, WEST III and WEST IV’s ability to make distributions and pay dividends to the Company is subject to the prior payments of their debt and other obligations and their maintenance of adequate reserves and capital. Under WEST II, WEST III and WEST IV, cash is collected in a restricted account, which is used to service the debt and any remaining amounts, after debt service and defined expenses, are distributed to the Company. Additionally, a portion of maintenance reserve payments and lease security deposits are formulaically accumulated in restricted accounts and are available to fund future maintenance events and to secure lease payments, respectively. The WEST II, WEST III, and WEST IV indentures require that a minimum threshold of maintenance reserve and security deposit balances be held in restricted cash accounts.

In September 2016, the Company entered into an amendment (the “Amendment No. 2”) to the Amended and Restated Trust Agreement of WEST II, as amended by Trust Amendment No. 1, dated September 2012. The Amendment No. 2 allows the Company to make additional equity contributions to fund engine maintenance expenses, to make up shortfalls in required net sale proceeds from engine dispositions and to provide additional funds in the acquisition of replacement engines for WEST II. These potential future equity contributions by the Company are voluntary. The Amendment No. 2 also increases the percentage of WEST II engines subject to disposition and modifies certain concentration limits.

In July 2014, the Company closed on a loan with a ten year term totaling $13.4 million. During 2016, the Company closed on two additional loans totaling $4.7 million, repayable over the same initial ten year term. The interest is payable at fixed rates ranging from 2.60% to 2.97% for the initial five years of the loan term and principal and interest is paid monthly. The loans provided 100% of the funding for the purchase of a corporate aircraft and subsequent modifications and upgrades. The balance outstanding on these loans was $10.9 million and $12.7 million as December 31, 2018 and December 31, 2017, respectively.

In January 2018, the Company repaid an existing loan at the maturity date. The loan was secured by three engines.