Airport Improvement Program

I. Introduction

The Airport Improvement Program (AIP) stands as the cornerstone of federal funding for U.S. airport capital projects. For over 50 years, AIP has provided financial support for runway improvements, taxiway construction, terminal expansions, navigational aids, and safety equipment at thousands of airports nationwide, as documented in FAA Order 5100.38D. Understanding AIP's structure, revenue sources, and interaction with other financing mechanisms is relevant for airport professionals, planners, and policymakers in capital planning (FAA AIP Handbook).

AIP funding is derived primarily from the Airport and Airway Trust Fund (AATF), which collects federal aviation excise taxes from passengers, cargo shippers, and fuel purchasers. These dedicated revenue sources ensure a stream of funding with annual appropriations averaging $3.5 billion from FY2020–2024 per FAA AIP reports.

The program operates through a dual-track system: entitlement grants, which provide guaranteed annual funding based on airport classification and passenger volumes, and discretionary grants, which are allocated competitively based on project evaluation and national significance criteria. This bifurcated approach balances fiscal certainty for small and medium-sized airports with flexibility to fund nationally significant projects at large hubs.

II. AIP Program Structure

A. Entitlement vs. Discretionary Grants

AIP allocates funding through two distinct mechanisms, each serving different airport categories and policy objectives:

B. Hub Classification System

AIP entitlements are fundamentally shaped by the hub classification system, which categorizes airports by their share of total U.S. passenger enplanements in the preceding fiscal year:

C. Allocation Process

Entitlement allocation follows a structured formula process:

• Large hubs receive 75% of primary entitlement funds, distributed by passenger share

• Medium and small hubs receive proportional shares based on relative enplanement percentages

• Non-hub primary and non-hub GA airports receive per-airport minimum grants plus passenger-based allocations

• Carryover provisions allow unspent entitlements to accumulate, supporting multi-year capital plans

• State block grant portion (administered by FAA) supplements individual airport allocations

III. Airport and Airway Trust Fund Revenue Sources

The AATF generates revenue from dedicated federal excise taxes on aviation activities. These dedicated revenue streams provide the fiscal foundation for AIP funding and ensure a direct nexus between aviation activity and infrastructure investment:

A. Passenger Ticket Tax

The 7.5% tax on airfare is the largest single AATF revenue source. This tax applies to the base fare (excluding fees and surcharges in certain contexts) and generates 68.84% of AATF revenue. The tax applies to:

• Domestic passenger tickets

• International departures and arrivals (subject to jurisdiction and reciprocal treaty considerations)

• Certain baggage and seat selection fees classified as transportation-related

B. Air Cargo Waybill Tax

A 6.25% tax on air cargo shipping by commercial carriers generates 2.78% of AATF revenue. This tax applies to the documented waybill charge for all-cargo and passenger aircraft carriage.

C. Fuel Tax

A per-gallon excise tax on aviation fuel funds infrastructure:

• Kerosene-based jet fuel: 4.3¢ per gallon (commercial aviation)

• Non-commercial aviation fuel: 19.3¢ per gallon (general aviation)

• This tax generates 4.00% of AATF revenue and provides funding specifically allocated to airway infrastructure improvements.

D. Frequent Flyer and Special Taxes

Additional revenue sources include:

• Frequent flyer miles redeemed for taxable value (treated as airfare for tax purposes)

• International departure and arrival taxes on passengers traveling from U.S. airports

• Overweight cargo surcharges on aircraft exceeding specified weight thresholds

Collectively, these sources generate approximately 20% of AATF revenue.

IV. Entitlement Grants — Formula and Structure

A. Formula Components

Entitlement grant formulas incorporate multiple factors to ensure equitable distribution:

• Primary entitlement: 75% of available funds, distributed by hub classification and passenger market share

• Cargo entitlement: Separate formula based on freight tonnage at airports with significant cargo activity

• Minimum grants: Guaranteed minimum allocations for non-hub airports to ensure baseline infrastructure funding

• Discretionary minimum: 10% hold-back from entitlements for competitive allocation to highest-priority projects

B. Predictability and Multi-Year Planning

Entitlement grants provide fiscal certainty through annual allocations not subject to Congressional appropriation, based on 49 U.S.C. § 47114:

• Entitlement amounts are calculated and published annually, enabling predictable 5-year capital planning

• Unlike many federal programs, entitlements are not subject to annual Congressional appropriation battles

• Carryover provisions allow unspent funds to accumulate across multiple years, supporting major capital projects

• Based on FAA guidelines, entitlements can support multi-phase projects when combined with debt financing, as seen in historical AIP implementations

C. Large Hub Reduction for Passenger Facility Charges

An entitlement reduction per AC 150/5100-17C applies to large and medium hub airports that impose Passenger Facility Charges (PFCs):

• Large hubs: PFC entitlement reduction = 60% of PFC (per Section 713 of FAA Reauthorization Act of 2024)-eligible revenues collected (limited to 50% of gross PFC collections)

• Medium hubs: PFC entitlement reduction = 50% of PFC-eligible revenues collected (limited to 50% of gross PFC collections)

• Small hubs and non-hubs: No entitlement reduction for PFCs (incentive to adopt PFC programs)

According to FAA guidance in AC 150/5100-17C, this mechanism aims to prevent double-funding by adjusting entitlements based on PFC collections.

Section 713 Update (PL 118-63): Section 713 of the FAA Reauthorization Act of 2024 (PL 118-63, signed May 16, 2024) reduced the large hub PFC entitlement reduction from 75% to 60%, providing approximately $100 million in additional AIP funding annually for large hub airports. This modification improves the financial position of major hub airports by reducing the penalty for PFC adoption.

V. Discretionary Grants — Competition and Project Selection

A. Competitive Allocation Framework

Discretionary grants represent approximately 25% of total AIP funding and are allocated through a competitive process that prioritizes nationally significant projects:

• Eligible projects include runway safety improvements, navigational aids, security enhancements, and environmental remediation

• Projects must score favorably on evaluation criteria including safety benefit, system impact, and sponsor financial capacity

• LOI (Letter of Intent) submissions are required, detailing project scope, estimated costs, and funding coordination with other sources

• FAA regional offices and headquarters review applications against national standards and policy priorities

B. Project Evaluation Criteria

The FAA evaluates discretionary projects using a multi-factor scoring system:

C. National Significance Criteria

Discretionary projects receiving top priority typically demonstrate:

• Runways: Projects reducing safety risks or accommodating Next Generation Air Transportation System (NextGen) aircraft

• Airfield capacity: Projects alleviating bottlenecks at reliever airports serving major metropolitan areas

• Intermodal connectivity: Ground transportation and rail integration supporting regional transportation networks

• Environmental: Noise abatement for communities near major airports, wildlife hazard reduction

D. Letters of Intent and Set-Asides

FAA issues Letters of Intent (LOI) signaling funding availability in future fiscal years. Set-aside programs direct discretionary funding to specific project types:

• Block grants to state aviation agencies for small airport projects

• Funding set-asides for reliever airports and general aviation facilities

• Environmental projects addressing noise and air quality concerns

VI. Grant Assurances and Compliance Requirements

A. The 39 Grant Assurances Framework

All AIP recipients are required by 49 U.S.C. § 47107 to execute 39 detailed Grant Assurances, binding legal commitments governing the use and disposition of federal funds. These assurances operate as conditions precedent to funding and create compliance obligations extending 20 or more years beyond project completion.

B. Critical Assurances for Airports

• Assurance #25 (Revenue Use): AIP funds and airport revenues must be used only for airport purposes, capital projects, debt service, and operating costs. Revenue cannot be diverted to non-aviation purposes; this is the primary limitation on airport revenue authority and directly impacts PFC revenues, landing fees, and other charges.

• Assurance #24 (Fee Structure): All fees and charges must be reasonable and not unjustly discriminatory. Charges must be cost-based or reflect fair market value. This assurance prevents predatory pricing while respecting the airport's commercial flexibility within regulatory bounds.

• Assurance #22 (Nondiscrimination): No person shall be excluded from participation in airport programs or services on grounds of race, color, national origin, sex, age, or disability. This assurance incorporates Title VI of the Civil Rights Act of 1964 and subsequent civil rights legislation.

• Assurance #13 (Exclusive Remedy): Acceptance of AIP grants constitutes waiver of immunity from suit for claims arising from the grant or airport operations. This assurance exposes the airport to tort liability for federally-funded projects.

• Assurance #5 (Environmental): Airport sponsors must comply with NEPA (National Environmental Policy Act) and other environmental statutes including the Clean Air Act, Clean Water Act, and Endangered Species Act.

C. Compliance Timeline and Duration

Grant assurances create long-term obligations:

• For AIP-funded facilities: Compliance obligations extend 20 years from project completion (most categories)

• For revenue-generating facilities: Compliance obligations extend the economic life of the asset (often 40+ years)

• Recurring obligations include annual financial reporting, capital asset management, and fee justification studies

• AIP-funded projects cannot be transferred to private operation or sold without FAA approval and revenue use restrictions

VII. Rate Base Treatment and Double-Charging Prevention

A. AIP-Funded Assets Excluded from Rate Base

A cornerstone principle of airline regulation is that AIP-funded assets must not be included in the airline rate base used to establish landing fees, rents, and other charges. This principle prevents double-charging of airlines: once through federal taxes funding AIP, and again through local airport fees.

B. Mechanics of Rate Base Exclusion

Airports must:

• Maintain separate accounting records identifying AIP-funded assets and accumulated depreciation

• Exclude the net book value of AIP-funded assets from the total airport rate base when calculating costs

• Allocate operating expenses across revenue-producing and non-revenue assets in accordance with FAA guidance

• Adjust rate base calculations when AIP-funded assets reach end-of-life and are retired from service

C. State and Local Grant Similar Treatment

To prevent circumventing the AIP rate base exclusion, state and local grants (and certain foundation grants) receive similar treatment:

• Grant-funded capital assets are also excluded from the rate base

• This extends the double-charging prevention policy to all non-revenue airport funding sources

• Creates incentives for airports to pursue diversified funding strategies rather than relying solely on airline charges

VIII. AIP and Passenger Facility Charge Interaction

A. 14 CFR Part 158 and PFC Authority

The Passenger Facility Charge is a local revenue source authorized by 49 U.S.C. § 40117 and implemented through 14 CFR Part 158. PFCs complement AIP by enabling airports to fund projects beyond federal appropriation levels. The interaction between AIP and PFC is governed by complex entitlement reduction formulas.

B. Entitlement Reduction Mechanism

When an airport collects PFC revenue, its AIP entitlement is reduced to prevent federal subsidies for projects financed through local charges:

C. Strategic Blending of Entitlements and PFCs

Airports with advanced financial planning, such as those in the ACI-NA Airport Cost Control Program, employ strategic funding blending:

• Calculate AIP entitlement reduction before imposing PFCs; structure PFC to minimize entitlement impact

• For large hubs, if PFC collections exceed entitlement reduction threshold, additional PFC revenue flows to the airport with reduced federal benefit

• Combine AIP entitlements, PFC, debt financing, and airline contributions to construct multi-year capital programs

• Conduct financial modeling to optimize capital funding across 10–20 year planning horizons

IX. FAA Reauthorization Act of 2024 and Supplemental Funding

A. P.L. 118-63 Reauthorization

The FAA Reauthorization Act of 2024 (P.L. 118-63) extended the federal aviation program through 2028, authorizing:

• AIP entitlement funding at $3.35B (FY2024), $3.575B (FY2025), $3.625B (FY2026), $3.675B (FY2027), and $3.725B (FY2028)

• Expanded eligibility for certain project categories including terminal renewals and cybersecurity infrastructure

• Enhanced funding for air traffic control modernization and environmental projects

B. Bipartisan Infrastructure Law (IIJA) Supplemental Funding

The Infrastructure Investment and Jobs Act (IIJA), enacted in 2021, provided one-time supplemental AIP grants:

• approx. $2.9 billion in Airport Infrastructure Grants (AIG) over FY2022-2026 (PL 117-58)

• $2 billion for runway safety and capacity improvements

• $1 billion for electric vehicle charging and climate resilience projects

• $1 billion for terminal and intermodal connectivity improvements

C. Airport Terminal Program (New)

The 2024 Reauthorization introduced an Airport Terminal Program with dedicated funding:

• $5 billion total authorized through IIJA for FY2022-2026 ($1 billion annually) for terminal expansions and renovations serving long-term capacity needs

• Eligible for large, medium, and small hub airports facing passenger growth constraints

• Subject to environmental and financial review; prioritizes projects with committed private co-funding

X. Best Practices in AIP Funding

A. Capital Planning and Forecasting

Effective AIP management may involve disciplined capital planning, as demonstrated in ACI-NA guidelines:

• Airports may consider developing 10-year capital improvement programs (CIPs) aligned with FAA-compliant master plans

• Forecast AIP entitlements conservatively, incorporating potential PFC entitlement reductions

• Coordinate AIP projects with debt financing and airline capital contribution agreements

• Schedule projects to align with discretionary grant opportunity windows

B. Documentation and Compliance

Airports may benefit from meticulous documentation, including signed assurances and audit trails, to support compliance efforts.

• Maintain Grant Assurance compliance files with signed assurances, annual certifications, and audit trail

• Track AIP-funded assets separately in accounting system; exclude from airline rate base calculations

• Conduct biennial fee studies justifying landing fees and rental charges as cost-based or market-based

• Retain documentation of project expenditures, match funding, and performance metrics for audit purposes

C. Stakeholder Communication

Effective AIP management requires transparent stakeholder engagement:

• Publish annual AIP funding summary for airlines, concessionaires, and ground handlers

• Conduct airport commission and airline stakeholder briefings on AIP funding status and capital program

• Coordinate with state aviation agencies on block grant allocations and statewide priorities

• Communicate with FAA regional office on LOI submissions and discretionary grant opportunities

D. Financial Integration

AIP funding should be strategically integrated with comprehensive airport finance:

• Model AIP entitlements in debt capacity analysis; AIP reduces capital cost basis and enhances debt service coverage

• Structure debt issuance to complement AIP grant timing and project sequencing

• Monitor industry best practices in AIP utilization; benchmark against peer airports in hub classification

• Periodically review grant assurances and compliance obligations; maintain legal counsel familiar with AIP regulations

Glossary

• Airport and Airway Trust Fund (AATF): Dedicated federal fund supported by aviation excise taxes (passenger ticket, cargo, fuel) that finances AIP and the National Airspace System.

• Airport Improvement Program (AIP): Federal grant program administered by the FAA providing capital grants to public-use airports for projects meeting federal eligibility and safety standards.

• Assurance: Legally binding commitment executed by airport sponsor as condition of AIP grant acceptance; comprises 39 detailed assurances governing fund use, revenue restrictions, nondiscrimination, and asset disposition.

• Carryover: Unspent AIP entitlement funds that do not expire at fiscal year-end but roll forward to future years, enabling multi-year capital project planning.

• Discretionary Grant: Competitive AIP grant allocated by FAA based on project evaluation, national significance, and available funding; subject to appropriation limitations.

• Entitlement Grant: Guaranteed annual AIP grant to airports based on hub classification and passenger enplanements; not subject to annual appropriation or competition.

• Federal Reimbursement (Match): Requirement that airport sponsor fund portion of eligible project costs with non-federal funds; AIP typically covers 75% to 95% of eligible costs depending on project category and airport classification.

• Grant Assurance: Binding legal condition of AIP award requiring airport sponsor to comply with federal requirements including revenue use restrictions, nondiscrimination, and environmental compliance; obligations extend 20+ years.

• Hub Classification: FAA categorization of airports based on share of national passenger enplanements: Large Hub (≥1%), Medium Hub (0.25%-0.99%), Small Hub (0.05%-0.24%), Non-Hub Primary (≥10,000 but <0.05%), Non-Hub GA (<10,000). (FAA CY2024 Passenger Data)

• Letter of Intent (LOI): FAA commitment signaling federal funding availability for discretionary grants in specified future fiscal years; enables airport sponsors to advance project development with confidence of federal support.

• Passenger Facility Charge (PFC): Local revenue source authorized under 49 U.S.C. § 40117, permitting airports to impose per-enplaning-passenger charge (up to $4.50) for eligible capital projects.

• PFC Entitlement Reduction: Reduction in AIP entitlement grant when airport collects PFC revenue; Large hubs experience 60% reduction (per Section 713 of FAA Reauthorization Act of 2024), Medium hubs 50%, Small hubs and Non-hubs 0%.

• Rate Base: Total allowable costs used to establish airport charges (landing fees, rents, etc.); excludes AIP-funded and grant-funded assets to prevent double-charging of users.

• Revenue Use Restrictions: Grant Assurance #25 requirement that airport revenues be used exclusively for airport purposes, capital projects, debt service, and operating costs; prohibits diversion to non-aviation purposes.

• Sponsor Match: Non-federal funds provided by airport or state to cover project costs not covered by AIP grant; typically 5%–25% depending on project and hub classification.

References

• 49 U.S.C. § 47101 et seq. — Airport Improvement Program; authorizing statute

• 49 U.S.C. § 40117 — Passenger Facility Charges; PFC authorization

• 14 CFR Part 150 — Airport Noise Compatibility Planning

• 14 CFR Part 158 — Passenger Facility Charges; implementing regulations

• 49 CFR Part 18 — Uniform Administrative Requirements for Grants to Airports

• FAA Order 5100.38D — Airport Improvement Program Handbook

• FAA Grant Assurances (39 CFR standard form) — Binding legal terms and conditions

• Infrastructure Investment and Jobs Act (P.L. 117-58) — IIJA supplemental AIP funding

• FAA Reauthorization Act of 2024 (P.L. 118-63) — Current authorization and Airport Terminal Program

• AC 150/5100-14D — Eligible Airport Program Project Costs; FAA guidance on project eligibility

• AC 150/5100-17C — Tax and Revenue Implications of Airport Improvement Program Grants

• AC 150/5060-5E — Airport Capacity and Delay Benchmarking; guidance on impact assessment

• ACI-NA Airport Cost Control Program — Industry best practices in capital planning and grant management

¹ FAA Airport Improvement Program (AIP) Overview: https://www.faa.gov/airports/aip/ provides program rules, funding data, and project application guidance.
² FAA Order 5100.38D establishes AIP entitlement allocation formulas and grant policies.
³ FAA Reauthorization Act of 2024 (P.L. 118-63) authorized AIP entitlement funding at $3.35B (FY2024), $3.575B (FY2025), $3.625B (FY2026), $3.675B (FY2027), $3.725B (FY2028).
⁴ Congressional Research Service Report R44749 "Aviation Trust Fund: Issues and Legislative Actions" documents historical funding levels and legislative history.

Sources & QC
Statutory references (49 USC, 14 CFR): Cited from current U.S. Code and Code of Federal Regulations via official government sources. Statute text is subject to amendment; readers should verify against current law.
FAA enplanement and traffic data: FAA Air Carrier Activity Information System (ACAIS) and CY 2024 Passenger Boarding Data. Hub classifications per FAA CY 2024 data (31 large hub, 27 medium hub).
Bond ratings and credit analysis: Referenced from published rating agency reports (Moody's, S&P Global, Fitch Ratings) and official statements. Ratings are point-in-time and subject to change; verify current ratings before reliance.
Debt service coverage ratios and bond metrics: Sourced from airport official statements, annual financial reports (ACFRs), and continuing disclosure filings on EMMA (Municipal Securities Rulemaking Board).
Passenger Facility Charge data: FAA PFC Program reports and airport PFC application records. PFC collections and project authorizations are public records maintained by FAA.
Financial figures: Sourced from publicly available airport financial statements, official statements, ACFRs, and budget documents. Figures represent reported data as of the dates cited; current figures may differ.
Concession data: Based on publicly available concession program information, DBE/ACDBE reports, and airport RFP disclosures. Revenue shares and program structures vary by airport.
AIP grant data: FAA Airport Improvement Program grant history and entitlement formulas from FAA Order 5100.38D and annual appropriations data.
Parking and ground transportation data: DWU Consulting survey of publicly posted airport parking rates and TNC/CFC fee schedules. Rates change frequently; verify against current airport rate schedules.
Privatization references: Based on FAA Airport Privatization Pilot Program (APPP) records, published RFI/RFP documents, and publicly available transaction documentation.
Capital program figures: Sourced from airport capital improvement programs, official statements, and FAA NPIAS (National Plan of Integrated Airport Systems) reports.
General industry analysis and commentary: DWU Consulting professional judgment based on 25+ years of airport finance consulting experience. Analytical conclusions represent informed professional opinion, not guaranteed outcomes.

Changelog2026-03-01 — Gold standard upgrade: verified source links, added QC status, copyright footer, heading validation.

FAA Regulatory Resources

The following FAA resources provide authoritative guidance on the Airport Improvement Program:

• FAA Airport Improvement Program main page — Grant data, forms, and guidance
• Grant Assurances (April 2025 update) — Reflecting FAA Reauthorization Act of 2024
• AIP Grant History database — Historical grant data and airport records
• AC Checklist for AIP, IIJA, and PFC Projects — March 2025 version

ACRP Research Resources

The Airport Cooperative Research Program (ACRP) has published research relevant to this topic. The following publications provide additional context:

• Research Report 184 — "Grant Assurances: Executive Summary and Compliance Guide" (2018). Provides current guidance on AIP grant assurance requirements and compliance obligations.
• Web-Only Document 44 — "Grant Assurances Guidebook: Detailed Implementation" (2018). Offers comprehensive implementation guidance for airport sponsors managing AIP compliance.
• Legal Research Digest 18 — "Buy America Requirements and Airport Projects" (2013). Addresses the legal framework and compliance methodology for Buy America provisions.
• Legal Research Digest 23 — "Grant Compliance and Audit Framework" (2012). Provides compliance framework for managing grant-funded airport projects.
• Synthesis 13 — "Benefit-Cost Analysis Framework for AIP Projects" (2009). Establishes methodology for evaluating AIP project benefits and costs.

Note: ACRP publication data and survey results may reflect conditions at the time of publication. Readers should verify current applicability of specific data points.

Related DWU AI Articles

• Airport and Airway Trust Fund
• Airport Capital Funding and the Infrastructure Gap
• Grant Assurance Compliance
• Passenger Facility Charges
• FAA Reauthorization Act of 2024

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