4. Notes Payable and Accrued Interest At September 30, 2018 and December 31, 2017, the Company's notes payable and accrued interest consisted of the following: September 30 , 2018 December 31 , 2017 Credit Facility: Principal $ 130,800,000 $ 134,000,000 Unamortized debt issuance costs (1,078,900 ) (2,216,000 ) Accrued interest 204,800 278,900 Special purpose financing: Principal 10,304,700 13,511,900 Accrued interest 16,600 23,400 $ 140,247,200 $ 145,598,200 (a) Credit Facility The Company's $170 million Credit Facility is provided by a syndicate of banks and is secured by all of the assets of the Company, including its aircraft and engine portfolio, except for the aircraft that serve as collateral for the Company's SPE Financing. The Credit Facility, which expires on May 31, 2019, can be expanded to a maximum of $180 million. The Company is negotiating with lenders for an extension of the Credit Facility and a new non-recourse term loan that would be secured by certain of the regional jet aircraft in its portfolio, and expects these transactions, if completed, to close prior to the expiration of the current credit facility . The Company was not in compliance with the interest coverage, debt service coverage and revenue concentration covenants under the Credit Facility at September 30, 2018. The Company obtained a waiver from the Credit Facility lenders in November 2018 for the September 30, 2018 non-compliance. There were no fees or penalties related to the waiver. In addition, based on appraisals obtained in October 2018 for four assets held for sale, the Company had a borrowing base deficiency of approximately $1,400,000 at September 30, 2018. The Company cured the deficiency in October by making a principal payment of $2,000,000 on the Credit Facility. The Company was in compliance with all covenants under the Credit Facility at December 31, 2017. The unused amount of the Credit Facility was $39,200,000 and $36,000,000 as of September 30, 2018 and December 31, 2017, respectively. The weighted average interest rate on the Credit Facility was 5.61% and 5.21% at September 30, 2018 and December 31, 2017, respectively. (b) SPE Financing In August 2016, the Company acquired two regional jet aircraft using cash and financing separate from its Credit Facility. The separate SPE Financing resulted in note obligations of $9,805,600 and $9,804,300, which are being paid from a portion of the rent payments on the related aircraft leases through October 3, 2020 and November 7, 2020, respectively, and which bear interest at the rate of 4.455% per annum. The borrower under each note obligation is the special purpose entity that owns each aircraft. The notes are collateralized by the aircraft and are recourse only to the special purpose entity borrower and its aircraft asset, subject to standard exceptions for this type of financing. Payments due under the notes consist of quarterly principal and interest. The combined balance of the principal amount and accrued interest owed on these notes at September 30, 2018 and December 31, 2017 was $10,321,300 and $13,535,300, respectively.