4. Debt Obligations

Debt obligations consisted of the following:


	September 30,		December 31,
	2018		2017
	(in thousands)
Credit facility at a floating rate of interest of one-month LIBOR plus 2.0% at September 30, 2018, secured by engines. The facility has a committed amount of $890.0 million at September 30, 2018, which revolves until the maturity date of April 2021	$	466,000	$	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		326,759		—
WEST IV Series B 2018 term notes payable at a fixed rate of interest of 5.44%, maturing in September 2043, secured by engines		46,680		—
WEST III Series A 2017 term notes payable at a fixed rate of interest of 4.69%, maturing in August 2042, secured by engines		279,382		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		39,953		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		243,221		259,022
Note payable at fixed interest rates ranging from 2.60% to 2.97%, maturing in July 2024, secured by an aircraft		11,388		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
		1,413,383		1,103,743
Less: unamortized debt issuance costs		(21,270)		(18,338)
Total debt obligations	$	1,392,113	$	1,085,405

Principal outstanding at September 30, 2018, is repayable as follows:


Year	(in thousands)
2018	$	13,812
2019		55,380
2020		54,980
2021 (includes $466.0 million outstanding on revolving credit facility)		521,217
2022 (includes $173.8 million outstanding on WEST II Series A 2012 term notes)		207,733
Thereafter		560,261
Total	$	1,413,383

On August 22, 2018, Willis Engine Structured Trust IV (“WEST IV”), a direct, wholly-owned subsidiary of the Company closed its offering of $373.4 million in aggregate principal amount of fixed rate notes (the “WEST IV Notes”). The WEST IV Notes were issued in two series, with the Series A Notes issued in an aggregate principal amount of $326.8 million and the Series B Notes in an aggregate principal amount of $46.7 million. The WEST IV Notes are secured by, among other things, WEST IV’s direct and indirect interests in a portfolio of 55 engines and one airframe.

The Series A Notes have a fixed coupon of 4.75%, an expected maturity of approximately eight years and a final maturity date of September 15, 2043. The Series B Notes have a fixed coupon of 5.44%, an expected maturity of approximately eight years and a final maturity date of September 15, 2043. The Series A Notes were issued at a price of 99.99504% of par and the Series B Notes were issued at a price of 99.99853% of par. Principal and interest on the WEST IV Notes are payable monthly to the extent of available cash in accordance with a priority of payments included in the Indenture. Proceeds from asset sales by WEST IV will be used, at WEST IV’s election subject to certain conditions, to reduce WEST IV’s debt or to acquire other engines or airframes.

As of September 30, 2018, $373.4 million of the WEST IV Notes were outstanding. The assets of WEST IV are not available to satisfy the Company’s obligations other than the obligations specific to WEST IV. WEST IV is consolidated for financial statement presentation purposes. WEST IV’s ability to make distributions and pay dividends to the Company is subject to the prior payments of its debt and other obligations and WEST IV’s maintenance of adequate reserves and capital. Under 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 the 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 Company maintains a revolving credit facility to finance the acquisition of aircraft engines for lease as well as for general working capital purposes. The $890 million revolving credit facility has an accordion feature which would expand the entire credit facility up to $1 billion. The interest rate is adjusted quarterly, based on the Company’s leverage ratio, as calculated under the terms of the revolving credit facility.

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 September 30, 2018.