Why Airport Finance Has Three Separate Rule Books

Before diving into the documents, readers need to understand a critical aspect of airport finance: there is no single set of rules. An airport operates under three distinct frameworks with distinct definitions, math, and authorities:

• Accounting (GAAP) — governed by GASB standards. This is what the ACFR reports. Revenue, expenses, net position, depreciation — all defined by accounting rules. The ACFR is the airport's audited financial history under GAAP.
• Trust (Bond Indenture) — governed by the bond covenant. This is what the Official Statement defines. "Net revenues," "debt service coverage," "flow of funds" — these terms are defined by the indenture, not by GAAP. The OS is the airport's contract with bondholders.
• Rates & Charges (Airline Use Agreement) — governed by the AUA and FAA policy. This determines how costs are allocated to airlines — residual, compensatory, or hybrid — and who bears risk when conditions change.

Key difference: "Net revenues" under GAAP includes depreciation; "net revenues" under the indenture excludes it. "Operating expenses" in the ACFR follows GASB classification; "O&M expenses" in the flow of funds follows the indenture definition. Reading only the ACFR shows the accounting picture but misses the covenant constraints. Reading only the OS shows the debt structure but lacks audited verification of actual performance. Reading both documents is necessary because they describe different worlds — and the gaps between those worlds are where credit risk hides.

This guide is organized around that reality. We start with the two documents, then show what to extract from each, and conclude with how to cross-reference them to build a complete credit picture.

Two Documents, Two Purposes: ACFR Reports the Past, the OS Projects the Future

The ACFR/ACFR: What Happened

The Annual Financial Report (or ACFR in some states) is the airport's official audited financial statement, published 6–9 months after fiscal year-end. It contains:

• Auditor's Opinion — independent third-party verification that the statements fairly present the airport's financial position. Watch for emphasis-of-matter paragraphs signaling going concern risk, restatements, new accounting standards, or contingent liabilities.
• Management's Discussion & Analysis (MD&A) — management's narrative of what happened, why, and what challenges lie ahead. This is where management explains to readers what they want readers to know; it reveals priorities, concerns, and spin.
• Financial Statements (GAAP) — Balance Sheet (Statement of Net Position), Income Statement (Statement of Revenues, Expenses, Changes in Net Position), and supporting schedules, all in accordance with Governmental Accounting Standards Board (GASB) standards.
• Notes to Financial Statements — dense but essential: debt schedules, pension/OPEB obligations, contingent liabilities, lease obligations, covenant language, accounting policies, related-party transactions.
• Statistical Section — 10 years of unaudited historical data: enplanements, revenues by category, operating expenses, debt outstanding, coverage ratios, airline concentration, and demographic trends. This section is useful for comparing 10-year historical trends in enplanements, revenues, and debt ratios.

Where to find: EMMA (emma.msrb.org), airport websites, state auditor offices. Search by airport name or issuer.

The Official Statement: What's Projected

The Official Statement is the bond offering document filed on EMMA at the time of bond issuance. It describes the security for repayment and the framework governing rates and debt. It contains:

• Security and Source of Payment — which airport revenues are pledged to repay the bonds. The pledge determines credit quality: "all airport revenues" (broadest) vs. "aeronautical revenue only" (restrictive).
• Flow of Funds — the waterfall allocating revenue: operating costs → debt service → debt service reserve → renewal & replacement → subordinate obligations → general fund.
• Rate Covenant — the airport's binding commitment to set rates sufficient to achieve a minimum coverage ratio (based on 1.25x debt service). This is enforced—violation triggers default per the bond indenture. MSRB Rule G-32 requires disclosure of covenant violations, but does not define the default terms themselves.
• Additional Bond Test (ABT) — the test for whether the airport can issue new debt. based on requires that historical or projected revenues cover existing + new debt service at the minimum coverage ratio.
• Airline Use Agreement Summary — the rate-setting methodology (residual, compensatory, or hybrid) and key terms: cost centers, majority-in-interest thresholds, term and renewal date.
• Feasibility Study — traffic and revenue projections used to model debt service capacity. Compare to actual performance in the ACFR to assess management's forecasting accuracy.

Where to find: EMMA (always filed at bond issuance). Continuing disclosures (annual updates) also on EMMA. Older OSes may be on airport websites or require FOIA requests.

Why Both Matter

The ACFR answers "What happened?" The OS answers "What can happen?" The ACFR is backward-looking and audited; the OS is forward-looking and based on management assumptions. Cross-reference them to ask: Did traffic grow as the OS projected? Is the airport maintaining the coverage ratio required by covenant? Are airline rates tracking the increase foreseen in the feasibility study? The gap between projection (OS) and reality (ACFR) reveals whether management is optimistic or conservative, and whether the airport is on track.

The Five Things That Actually Matter in a ACFR

(a) Auditor's Opinion: Red Flags First

The auditor's opinion is two paragraphs. Analysts may find it useful to start with the auditor's opinion, as an unmodified opinion is standard—it means "we found no material misstatements and no going concern problems." However, watch for:

• Modified opinion (qualified, adverse, or disclaimer) — rare in airport finance (modified opinions occur in less than 1% of airport audits based on industry experience), signals material problems: inability to obtain evidence, scope limitation, or departures from GAAP. Requires immediate investigation.
• Emphasis-of-Matter Paragraphs — signal issues the auditor wants readers to understand:
  • Going Concern Uncertainty — the airport may not have sufficient liquidity or cash flow to meet obligations. Signals liquidity or solvency stress requiring immediate investigation. See AICPA guidance on going concern.
  • Restatement of Prior-Year Financials — prior numbers were wrong. How bad was the error? Was it accounting? Fraud? Carelessness? Read the MD&A for explanation.
  • New Accounting Standard Adoption — e.g., GASB 87 (Leases) or GASB 103 (Financial Reporting Model Improvements). These can materially increase reported liabilities and affect debt ratios. Read the note on the new standard to understand impact.
  • Contingent Liabilities or Litigation — the airport faces legal risk (environmental, employment, contractual). Jump to the contingent liabilities note to quantify.

⚠ Red Flag Check: If you see an emphasis-of-matter paragraph, turn directly to the relevant note or MD&A section. When an emphasis-of-matter paragraph flags an issue, verify the materiality level in the accompanying notes; the auditor's explicit mention typically signals material significance.

(b) Management's Discussion and Analysis: What Management Wants You to Know

The MD&A is 3–5 pages. Many practitioners overlook this section, missing an important source of management priorities and risk acknowledgment. The MD&A is where management signals priorities, acknowledges challenges, and frames the narrative of the airport's financial position.

Consider focusing on:

• What does management emphasize? Allocation of space is telling. Discussion of a new terminal project signals management sees growth opportunity. Explanation of why revenues fell may contextualize challenges.
• Does management acknowledge headwinds? Lost airlines, traffic decline, rising costs, debt service coming due? Transparent management addresses challenges. Some management narratives address challenges more explicitly than others; comparison to the income statement will clarify whether the narrative matches actual results.
• What's the spin? "Despite challenging conditions, the airport achieved stable revenues" can mean revenues were flat (good spin) or flat despite cost inflation (bad spin). Read the income statement to verify.
• Capital plans? What is management investing in? Are projects funded by debt (equity = no), by PFC (Passenger Facility Charges) (customer-funded), or by revenues (self-funded)? The funding mix reveals financial flexibility.
• Risk acknowledgment? Does management mention airline concentration, fuel price exposure, competitive threats, or staffing challenges? Transparent disclosure of risks signals sound governance.

⚠ Watch For: Compare the MD&A narrative to the income statement numbers. If MD&A says "revenues grew" but the income statement shows flat revenues (with one large concession contract starting mid-year), the growth was one-time, not structural. If MD&A says "we achieved stable coverage" but coverage fell from 1.35x to 1.25x, the airport is trending toward covenant minimum.

(c) Statement of Revenues, Expenses, and Changes in Net Position: The Income Statement

This is the airport's profit-and-loss statement (technically "changes in net position" under GAAP). It shows how the airport generated cash for debt service and reserves. Focus on four line items:

Debt Service Coverage Ratio (DSCR) Calculation

DSCR = Net Revenues (per indenture definition) ÷ Debt Service = Coverage Ratio

This is the single most important metric in airport credit analysis. A 1.25x ratio means for every dollar of debt service due, the airport generates $1.25 in net revenues. Below 1.25x, the airport is in stress (or will breach covenant). Above 1.50x, there's cushion for traffic declines. Covenant terms are defined by the individual bond indenture.

Important: At residual airports, DSCR is mechanically predetermined by the rate-setting formula — the coverage ratio is built into the airline rate calculation as an input cost. DSCR monitoring is primarily meaningful at compensatory airports, where the airport bears revenue risk and coverage depends on actual traffic and revenue performance.

Methodology Note: Different analysts define DSCR differently (some include PFC, some exclude it; some use deposit-basis, some use cash-basis). To ensure consistency, analysts may wish to locate the definition in the ACFR or OS notes and recalculate DSCR using the same components using the same components to ensure consistency.

(d) Notes to Financial Statements: Where the Detail Lives

The notes are dense and long, but they contain everything a credit analyst needs. One approach is to review these five notes:

1. Long-Term Debt Schedule

Find all outstanding bonds per GASB 34 disclosure requirements: issuance date, principal outstanding, coupon rate, maturity date, call date, and reserve fund requirement. Manually calculate debt service for the next 3 years. Ask:

• Is debt maturity spread evenly (lower refinancing risk) or bunched (refinancing cliff)?
• What are the coupon rates? Older bonds at 2–3% are refinancing candidates if rates fall. Newer bonds at 5%+ indicate tight market conditions at issuance.
• Is there a call date? Can the airport refinance early if rates fall?
• What is the reserve fund balance? Is it equal to MADS (maximum annual debt service) or 10% of par? If below MADS, the airport is under-reserved.

2. Pension & OPEB Obligations

What is the unfunded pension liability per GASB 68 (pension) and GASB 75 (OPEB)? What is annual required contribution? Is the airport contributing the full actuarial requirement or deferring?

• If unfunded liability is $50M and annual contribution is $3M, the airport will take 17 years to catch up—during which every dollar goes to the past, not the future. This limits financial flexibility.
• GASB 103 (effective fiscal years beginning after June 15, 2025) improves the financial reporting model, including MD&A requirements and proprietary fund statement presentation. Pension and OPEB liabilities remain governed by GASB 68 and GASB 75.
• Is the airport's contribution tracking the actuarial requirement? If lagging, underfunding is growing, and future contributions will rise.

3. GASB 87 Lease Obligations

If the airport leases equipment, land, or terminal space to concessionaries per GASB 87 (Leases, effective 2022), these leases are now capitalized on the balance sheet as lease assets and liabilities. Look for large lease obligations that reduce financial flexibility.

4. Contingent Liabilities

Environmental remediation, litigation, airline disputes, regulatory fines. Anything that might require spending. Read the summary, then assess:

• Is there a quantifiable liability (e.g., "estimated environmental remediation cost $20M")? If so, the airport has real financial risk.
• Is it reasonably possible but unquantified? This is lower risk, but still a flag.
• Is it remote? Don't worry about it.

5. Debt Covenants Summary

Find the language defining the rate covenant per the bond indenture and SEC Rule 15c2-12 disclosure requirements. What is the minimum coverage ratio? Is PFC included or excluded? What defines "Net Revenues"? Does it include all concession revenue or only airline-related revenue? This definition determines how tight the covenant is.

Coverage Analysis: If the airport's current coverage is exactly at the covenant minimum (1.25x), any traffic decline means breach. If coverage is 0.25x above minimum (1.50x vs. 1.25x), there is cushion for volatility. Compare historical coverage to current coverage—is it trending up or down?

(e) Statistical Section: 10-Year Trends

The statistical section is not audited, but it is valuable. It contains 10 years of unaudited historical data. Read these tables:

• Enplanements and Revenue Passengers — is traffic growing, stable, or declining? By how much annually? A decline of 2–3% annually over 5 years suggests structural headwinds (airline capacity cuts, hub consolidation, competitive pressure). Growth of 3–5% suggests the airport is competitive.
• Revenues by Category — aeronautical, concession, parking, rental car, other. Are any categories growing while others decline? (Possible mix shift—more valuable to airport if aero grows and less valuable if parking revenue grows as % of total.)
• Operating Expenses Trend — are expenses growing faster than revenue? (Margin compression is a potential indicator.)
• Debt Outstanding — total debt, and debt-to-revenue ratio. Is the airport issuing new debt every year (growing debt burden) or retiring debt (improving use)? Is debt-to-revenue stable (good) or rising (bad)?
• Coverage Ratios, 10-Year Trend — this is critical. A declining 10-year coverage trend is a credit warning. Improving coverage trend is a strength. A coverage ratio that dropped sharply in one year (usually a recession year like 2009 or 2020) but recovered is normal. But structural decline is a potential concern.
• Debt Service Requirements, Next 10 Years — when is the big refinancing? If principal payments are bunched in years 8–10 and the airport doesn't have a refinancing plan, there's refinancing risk.
• Top Airlines — concentration risk. If United is 40% of passengers and cuts its hub, what happens to the airport? Single-airline dependence is high risk.

Coverage Trend Analysis: Assess whether the airport is growing into its debt (coverage stable or improving) or shrinking into it (coverage declining). Coverage declined preceding downgrades in 12 of 15 cases (S&P airport ratings 2019-2024).

The Five Things That Actually Matter in an Official Statement

(a) Security and Source of Payment: What's Actually Pledged?

The OS always states upfront which revenues are pledged to repay bonds per SEC Rule 15c2-12 and MSRB Rule G-32 disclosure standards. This determines credit quality. Common pledges:

• "All Airport Revenues" — the broadest pledge, covering 100% of revenues per indenture (e.g., ATL OS 2023). Includes aero, concessions, parking, rental cars, everything.
• "Net Revenues" — total airport revenue minus operating expenses. This is tighter: if expenses rise, net revenue falls and coverage shrinks. Weaker than "all revenues."
• Aeronautical Revenue Only — a narrow pledge, sometimes used for separate airline facility bonds. Covers only landing fees, ramp fees, gate rent. Excludes parking, concessions, PFC. If aero revenue is 60% of total, this pledge covers only 60% of airport cash generation. Much weaker.
• Passenger Facility Charges (PFC) — sometimes separately pledged. Watch: is PFC included in the general revenue pledge or segregated for capital projects only?

Exclusions from Pledge: Some OS documents exclude parking, rental cars, ground transportation, PFC, or revenues from airport enterprises (hotel, parking garage). Exclusions shrink the revenue pool available for debt service. A pledge covering 60% of total revenues if aero is 60% of total is weaker than "all airport revenues."