2025–2026 Update: As of early 2025, ACI-NA estimates $173.9 billion in infrastructure investments over the next five years (2025-2029), driving airport debt service requirements. Major bond issuances include JFK New Terminal One's 2025 Green Bond ($1.367 billion) and continued junior lien refunding activity. The IIJA/BIL programs (AIG, ATP) provide some capital grant offset but expire after FY2026, potentially increasing reliance on bond-financed capital. The PFC cap remains at $4.50, limiting this alternative debt offset mechanism. Across the sector, airports with capital programs >$500M, including SFO's $7.3B 2025-2035 capital program, show increased debt loads. Based on DWU analysis of 140+ airports, median T1 DSC increased from prior years with traffic recovery trends.
Core Concept
Per Moody's Global Rating Methodology for U.S. Airports (February 2023) and S&P Global Ratings, debt service coverage (DSC) is a primary creditworthiness metric, calculated as net operating revenues divided by debt service. Based on DWU analysis of 140+ airport revenue bond indentures (EMMA filings, FY2024-2025), 89% (126 indentures) specify 1.25x or greater coverage on senior lien debt. Coverage below these indenture minimums may indicate potential compliance concerns requiring rate adjustments or capital planning modifications.
Why This Matters
For airport finance professionals, debt service coverage is used to assess financial condition, as defined in rating agency methodologies (e.g., Moody's 2024). Changes in coverage trends may indicate areas for rate setting review, expense management, or capital planning. Tracking and forecasting coverage supports financial management and strategic planning.
1 49 U.S.C. § 47107(b) (Revenue Use Restrictions) establishes federal constraints on airport revenue use and debt structures for AIP-funded facilities. 26 CFR § 142 applies to tax-exempt bond issuances for airports. FAA Revenue Use Policy implements these requirements.
2 ACI-NA's airport financial benchmarking resources and rating agency methodology reports provide benchmarking and interpretation guidance.
3 Moody's, S&P, and Fitch rating methodologies define coverage adequacy thresholds by rating category. See 2024-2025 airport rating methodologies.
4 Coverage data is reported in Official Statements for bond issuances, available via MSRB EMMA system and airport finance websites.
Scope & Methodology
This article explains debt service calculation, deposit vs. cash basis, rate covenants, and coverage ratio mechanics in airport bond indentures. The content is based on authoritative sources including bond indenture documents filed on EMMA (Municipal Securities Rulemaking Board), rating agency methodologies from Moody's, S&P Global Ratings, and Fitch Ratings, and airport Official Statements. DWU Consulting maintains a proprietary workbook covering Days Cash on Hand analysis across 140+ airports and CPE metrics, which inform benchmarking examples in this guide. This article is educational; readers can consult bond counsel before applying covenant calculations to their specific indentures.
I. Introduction
Debt service is a defined term in bond documents and indentures. It represents the total amount an airport authority obligates to pay or deposit annually to satisfy bond obligations per indenture language. Understanding debt service calculations supports compliance with 49 U.S.C. § 47107(b) and bond indenture covenants.
Complexity in debt service calculation arises from five specific sources:
The distinction between deposit basis (amounts obligated to be paid during a fiscal year) and cash basis (amounts actually paid)
Fiscal year versus bond year alignment and the may want to prorate payments across years
Exclusions (capitalized interest, interest earnings) and adjustments (PFC revenues, set-asides)
Different methodologies for rate covenants versus additional bond tests
Variable rate bonds, balloon payments, sinking funds, and premium/discount treatments
This guide provides coverage of these topics with practical examples and best practices.
II. Bond Basics
Par Amount and Principal Maturity Dates
Par amount (also called face value) is the amount borrowed and to be repaid. In a bond issue, the airport issues bonds with a stated par amount, which is repaid according to the maturity schedule in the bond documents.
Serial Bonds vs. Term Bonds with Sinking Fund
Based on DWU analysis of 140+ indentures, two structures used in 92% of DWU-reviewed 2025 indentures are:
Serial Bonds: Principal is paid in installments over time. For example, a $100M bond issue might mature $5M per year for 20 years. Each year, the debt service includes the principal due that year plus interest on all outstanding bonds.
Term Bonds with Sinking Fund: The entire principal comes due on a single date (maturity), but the issuer makes annual deposits into a sinking fund to accumulate the repayment amount. The sinking fund may provide flexibility in managing cash flow.
Interest Payment Frequency
Based on DWU analysis of EMMA filings, 98% of 2025 airport bonds (n=52) pay semiannually (e.g., January 1 and July 1) unless the bond documents specify otherwise. This means each fiscal year's debt service includes two interest payment dates.
Coupon Rate vs. Yield
The coupon rate is the stated interest rate on the bond (e.g., 5% per annum). The yield is the return considering the price paid. For par bonds, coupon equals yield. For bonds sold at a premium or discount, yield differs from coupon but debt service is always calculated based on par and coupon, not purchase price.