Support Activities for Air Transportation (U.S.) — NAICS 4881

A Histometrics rollup primer for both public-market and private investors, synthesized from the two child-industry primers and our federal ground-truth statistics for this level.

1. Overview

NAICS 4881 — Support Activities for Air Transportation is the federal statistical family for the private businesses that stand behind the airlines: the firms that run the airfields, service the aircraft, handle the bags and freight, fuel the private jets, and keep the traffic moving in the tower and in the air (NAICS is the North American Industry Classification System). It is the "picks-and-shovels" layer of U.S. aviation — recurring, often mandatory services sold into a cyclical airline and business-jet fleet [1][4][5].

The group has two children, and they divide the work cleanly by where the service happens:

• 48811 — Airport Operations: the places and the airspace — running civil airports (fueling, handling, baggage, cargo, concessions, terminals) and staffing air-traffic-control towers [4].
• 48819 — Other Support Activities for Air Transportation: the aircraft itself — independent maintenance, repair and overhaul (MRO), ground and ramp handling, de-icing and cleaning, aircraft testing and ferrying, and the fixed-base operators (FBOs) that fuel and hangar business jets [5].

Two facts shape everything below. First, the biggest operators of the airports-and-airspace side are governments, and governments are excluded from these statistics — almost every U.S. commercial airport is owned by a city, county, state, or public authority, and air-traffic control is run by the Federal Aviation Administration (FAA) [4][6]. Second, the aircraft-servicing side is genuinely private, market-facing, and where the group's only real listed pure-plays live. So the two children are not just different sizes — they are owned by different kinds of capital and reached through different instruments. That contrast is the point of this primer.

2. What's inside — the two children and how they differ

The family splits into a labor-heavy, government-anchored "run-the-airport-and-airspace" child (48811) and a larger, more capital-market-accessible "service-the-aircraft" child (48819). They share the same FAA regulator and the same cyclical demand, but as investments they behave very differently.

Share figures blend 2022 receipts with 2023 employment/establishment counts (see §3); the per-worker ratios are order-of-magnitude, not same-year.

The through-lines that unite them. Both children are essential, hard-to-replace aviation infrastructure with high entry barriers (airport leases, hangar scarcity, FAA certificates, trained labor). Both are shaped less by consumer markets than by federal aviation policy, FAA budgets, and flight volume. And in both, the largest and most valuable pieces are either governmental (airports, ATC) or privately held (FBO chains, terminal partnerships) — so the public-market investor is usually buying a proxy, not the asset.

The differences that matter for capital. They pull in opposite directions on the two things investors care about most:

• Where the money is vs. where the workers are. 48819 is the bigger revenue pool (~62%), but 48811 holds the majority of jobs (~58%). That flips because 48819's revenue is inflated by pass-through — FBOs resell fuel and MRO shops resell parts, so a dollar of receipts represents fewer hours of labor — while 48811 is packed with low-wage ground handling and concessions.
• What a worker is worth. 48819 pays roughly $73,000 a head (skilled A&P mechanics, engine technicians); 48811 pays roughly $39,000 (ramp, cleaning, concessions). Same industry group, nearly 2× the wage.
• Who you can actually buy. The aircraft-servicing child (48819) is the one with listed pure-plays and a clean private small-business path. The airport child (48811) is mostly government-owned at the core and private-equity-owned in its investable layers — you lend to it (muni bonds) or you buy the sponsor, but you rarely buy the airport.

Put bluntly: 48819 is the more investable, more disclosed, more revenue-heavy half; 48811 is the more labor-heavy, more government-anchored, more policy-driven half. Read the rollup figures below as a blend of the two, and always decompose them before drawing a conclusion.

3. How big it is (this level's rollup figures)

The figures below use OUR ingested federal-statistics extract for NAICS 4881, drawn from the Census Bureau's 2022 Economic Census concentration program (receipts and concentration) and 2023 County Business Patterns (CBP — establishments, employment, payroll).

Reference years differ — receipts and concentration are 2022, while employment and payroll are 2023 — so do not compare receipts against same-year payroll. Within their own years the figures imply roughly $8.4 million of receipts per firm, $5.6 million per establishment, and ~$53,000 of pay per employee — a blended average that sits between the low-wage 48811 and the skilled 48819, and belongs to neither.

The two children sum, but the concentration statistic misleads. The children add up almost exactly — establishments (2,585 + 4,237 = 6,822) and employees (142,448 + 103,177 = 245,625) reconcile to the penny, and receipts (~$14.5B + ~$23.7B) reconcile to ~$38.2B [3][4][5]. (Firm counts are the one exception: the children list 1,095 + 3,513 = 4,608 firms against a group total of 4,565, because a few dozen operators — mostly FBO and ground-handling companies that span both codes — are counted once at the group level.) But the HHI of 82.5 is lower than either child's (241 for 48811, 115 for 48819). Combining two industries whose leaders are different firms dilutes every share, so the blended number understates real concentration. Worse, it buries a genuine oligopoly: inside 48811 sits air-traffic control, where four contract-tower firms hold ~86% of the sliver [4]. Never read this group's concentration as one number — decompose it child by child, and within 48811, sub-child by sub-child.

The undercount is structural — and it cuts both ways. Census business statistics count private employer establishments; they largely exclude government entities, the self-employed, and nonemployer businesses [3]. That removes the two dominant operators of U.S. aviation infrastructure — public airport authorities and the FAA's air-traffic system — from the 48811 side [4][6]. On the 48819 side it removes the maintenance that airlines do in-house (counted under air transportation, not here), factory overhaul by original-equipment manufacturers (OEMs, in manufacturing code 336411), and fuel counted as wholesale (424720) — which is why one market-research house puts the broader "U.S. aircraft MRO market" near $51.7 billion in 2024 [10], far above the independent slice measured here. For scale on the other side, the trade group Airports Council International–North America (ACI-NA) estimates U.S. commercial airports support a $1.8 trillion total economic footprint [8] (a broad multiplier, not comparable to receipts). Treat NAICS 4881 as "the private, independent air-transport-services economy," not "U.S. aviation." OUR data do not report industry margins, capital spending, capacity utilization, or valuation multiples; where those appear below they come from the cited child primers and industry sources.

4. Investable universe — where value concentrates across the children

There is no single, clean, U.S.-listed way to own this group — and the two children fail that test for opposite reasons. 48811's core is governmental; 48819's core is private but fragmented.

48819 (the ~62% child) — this is where listed pure-plays exist. The clearest technical-aftermarket names are the independent MRO providers: StandardAero (NYSE: SARO), AAR Corp. (NYSE: AIR), and VSE Corporation (Nasdaq: VSEC), with adjacent handling/services exposure through ABM Industries (NYSE: ABM), SATS (SGX: S58, which owns Worldwide Flight Services), Agility Global (ADX: AGILITY, Menzies), and General Dynamics (NYSE: GD, via Jet Aviation) [5][11][12]. The bigger asset pools — FBO networks and ground handling — are largely private, owned by infrastructure and private-equity (PE) capital: Signature Aviation (Blackstone/GIP/Cascade), Atlantic Aviation (KKR), Modern Aviation, Million Air, Swissport, dnata, and PrimeFlight [5][9]. And the fragmented tail makes 48819 the one child with a real direct small-business path: a single repair station or FBO is a buyable asset.

48811 (the ~38% child) — the core is unbuyable; the exposure is indirect. No pure-play, U.S.-listed airport operator or air-traffic-control company exists. The economically important owners are governments (airport authorities; the FAA) or private capital in the layers on top [4][6]. Public-market investors reach it through: diversified parents with an airport-services arm (General Dynamics again, via Jet Aviation); the closest listed U.S.-terminal exposure (Ferrovial, Nasdaq: FER, in the JFK New Terminal One partnership); foreign-listed airport operators for genuine "own-the-airport" economics (Mexico's ASUR, NYSE: ASR, plus GAP, OMA, Europe's AENA, ADP, Fraport); and — for the ATC-modernization boom — the federal systems contractors that build FAA systems, RTX (NYSE: RTX) and Leidos (NYSE: LDOS), none of them pure-plays [4].

Watch the overlap so you don't double-count. FBOs and ground handling straddle the two children: the Census codes an FBO's fueling and aircraft handling as a support activity (48819/488190) but its airfield operation as airport operations (48811/488119), so a chain like Signature or Atlantic — and a handler like Menzies or WFS — can appear on both sides. The private-jet FBO layer and the ground-handling layer are best thought of as shared platforms that sit across the seam, not as belonging cleanly to one child.

The retail-accessible common denominator: municipal airport revenue bonds. Because the dominant operators on the 48811 side are governmental, the most direct way most investors can lend to U.S. aviation infrastructure is airport revenue bonds — municipal debt repaid from ring-fenced airport cash flows (§10) [16].

5. How the money works

Across the group there are four distinct economic engines, and they map onto the two children:

• Fuel margin (FBOs — spans both children). Buy jet fuel wholesale, sell it into the aircraft at a markup, so earnings scale with gallons uplifted × margin, plus hangar rent and ramp fees. A field with only one or two FBOs confers real pricing power — economics that look like toll-road real estate, which is why infrastructure funds pay billions for the networks [5][9].
• Labor-hours + parts markup (MRO — 48819). Bill technician hours at a shop rate plus a markup on parts, often under fixed-price scopes or "power-by-the-hour" agreements. Profit turns on skilled-labor productivity, bay utilization, work mix (engine and component overhaul is the high-value work), and turn-around time. Maintenance is mandatory on regulator-set schedules, which gives this engine an annuity-like resilience [5].
• Per-turn / per-flight handling (ground handling — spans both children). Thin-margin, high-volume, labor-intensive work priced per aircraft turn, flight, passenger, or bag under multi-year airline contracts. Scale, reliability, and safety records matter more than pricing power; wage inflation and contract retention dominate [5].
• Airport & airspace revenue (48811). Airport operators (mostly government authorities) split revenue into aeronautical (landing fees, gate and terminal rents) and non-aeronautical (parking, retail/food concessions, rental cars); big projects are funded by revenue bonds plus federal tools — Passenger Facility Charges (a per-passenger surcharge capped at $4.50) and Airport Improvement Program grants. Contract-tower operators earn essentially (towers under contract) × (staffing hours) × (rate), with controller labor the dominant cost and thin single-digit federal-services margins [4].

The useful metrics therefore differ by child. For 48811: passenger enplanements, aircraft movements, cargo landed weight, non-aeronautical revenue share, FBO fuel throughput, debt-service coverage, and — for ATC — contract backlog and recompete win rate. For 48819: fleet flight hours and cycles, aircraft age, engine shop-visit volume, bay/technician utilization, turn-around time, and contract retention. Neither child rewards traditional manufacturing measures like factory capacity utilization.

6. Demand drivers

The group shares one master driver — flight activity — that then splits into child-specific tailwinds.

• Passenger air-travel volume — enplanements track GDP, employment, and travel budgets; the master driver for airport operators, concessions, and passenger handling [8].
• Business- and private-jet activity — the lifeblood of FBOs (both children); U.S. private-jet departures reached roughly 2.63 million in 2025, up ~5% year-on-year and ~29% above 2019 [14].
• Aircraft age and airline outsourcing (48819) — Boeing/Airbus delivery backlogs keep older jets flying longer, and older jets need more maintenance; a multi-year engine shop-visit wave and continued airline outsourcing of non-core work feed the independent MRO and handling firms [5].
• Air-cargo and e-commerce — time-sensitive freight drives cargo handling and cargo-aircraft maintenance [5].
• The airport capital cycle and federal budget (48811) — U.S. airport capital spending hit a record ~$28 billion in fiscal 2025 against ~$174 billion of estimated five-year needs, and a $12.5 billion 2025 "brand-new air-traffic-control system" down payment (with ~$20 billion more identified) feeds the ATC side [8][13]. A chronic controller shortage keeps hiring, training, and contract-tower demand elevated [4].
• Winter weather and government readiness — de-icing and some government/military work add partly non-commercial demand [5].

Demand is durable but cyclical: ACI-NA reported North American passenger traffic slipped 0.7% in 2025, and the pandemic devastated ground handling — even a structurally growing sector has flat and down years [5][8].

7. Regulation

The whole group sits under one regulator — the FAA — but the touch-points differ by child.

• 48819 — certificated service providers. MRO shops must be certificated under 14 CFR Part 145 and may perform only rated work; mechanics hold Airframe & Powerplant (A&P) certificates; the Transportation Security Administration (TSA) governs worker access, the Occupational Safety and Health Administration (OSHA) covers ramp and hangar hazards, and the Environmental Protection Agency (EPA) regulates de-icing (glycol) discharges. Local airport "minimum standards" ordinances license who may operate an FBO or a handling business at each field. Regulation here is a cost, a barrier to entry, and — for credible incumbents — a moat [5][15].
• 48811 — regulated infrastructure and the regulator's own function. Commercial airports operate under Part 139 safety certificates; any airport that has taken federal grants is bound by Grant Assurances — most importantly that fees keep the airport self-sustaining and that all airport revenue stays on the airport (anti-diversion), the ring-fence that makes airport revenue bonds creditworthy [4][16]. The frozen $4.50 Passenger Facility Charge cap (unchanged since 2000) limits pricing flexibility. On the ATC side the FAA is unusual in both running air-traffic control and certifying its controllers; contract towers must clear a favorable benefit-cost test and staff to FAA standards, and recent oversight has tilted toward pulling some high-activity towers back in-house [4].
• Privatization is narrow on both sides. Full U.S. airport privatization is capped and lightly used, and the long-debated shift of ATC to an independent, user-fee-funded corporation has repeatedly failed in Congress [4][6]. Regulation protects incumbents across the group, but caps how much value private capital can extract and injects policy risk.

8. Consolidation

The group is fragmented but consolidating fast, through different mechanisms in each child.

• 48819 consolidates through M&A. The low HHI (~115) reflects thousands of small operators, yet the biggest platforms are rolling up the tail behind hard local barriers (airport leases, hangar availability, certifications, scarce labor): FBOs are being assembled by infrastructure and PE capital (Signature, Atlantic, Modern Aviation); independent MRO is scaling through IPOs and acquisitions (StandardAero, AAR, VSE); and ground handling is consolidating globally (SATS bought Worldwide Flight Services for ~€2.25B in 2023; Menzies bought G2 Secure Staff for ~$305M in 2025) [5][9][11][12]. The key structural threat is OEM encroachment into the profitable overhaul work [5].
• 48811 consolidates two ways. Its private layers consolidate through M&A — the same FBO and ground-handling roll-up plus a handful of concessions groups and infrastructure investors competing to design-build-finance-operate terminal public-private partnerships [4][9]. But its air-traffic-control sliver consolidates through government procurement, not mergers: a December 2024 recompete split roughly $1.4–1.5 billion across just four vendors, with who holds each tower set by FAA award [4]. The airport-operator core itself is a set of local monopolies — one dominant airport per metro — that cannot be bought because they are governmental.

Because FBO and ground-handling platforms span both children, the group's most active consolidators (Blackstone, KKR, Apollo, GIP/BlackRock, SATS, Menzies) are simultaneously buying assets coded on both sides of the seam.

9. Risks

• Cyclicality and shock exposure (whole group). Demand falls with recessions, fuel spikes, geopolitics, and travel shocks; COVID-19 hit ground handling and airport concessions at once.
• A two-sided labor problem. 48811 leans on low-wage, high-turnover ramp and concession labor; 48819 leans on a structural shortage of A&P mechanics — and the ATC sliver on a 3,000-plus certified-controller shortfall. Both wage inflation and skilled scarcity can absorb the benefit of higher volumes [4][5].
• Leverage and interest rates. PE- and infrastructure-owned FBO chains, ground-handling platforms, and terminal partnerships carry heavy debt; higher rates raise refinancing costs and compress equity returns [5].
• Single-customer and recompete risk (48811 ATC). Contract-tower revenue is tied to a few large FAA awards; losing a recompete — or the FAA converting a tower back in-house — materially hits a firm [4].
• OEM competition and fixed-price execution (48819). Original-equipment manufacturers are pushing into the profitable aftermarket, and fixed-price MRO scopes turn against operators when inflation outruns escalators [5].
• Fuel-margin dependence (FBOs, both children). Earnings lean on the into-plane fuel spread; fuel-price volatility, sustainable aviation fuel, and eventual electrification could pressure the core margin [5].
• Budget and political dependence (whole group). A government shutdown or continuing resolution can freeze FAA hiring and halt both airport grants and ATC modernization spending [4].
• Safety, environmental, and classification liability. A major accident, a glycol-discharge violation, or a misclassification finding can trigger investigations, penalties, and reorganizations [5][15].
• Data risk. The federal figures understate activity outside private employer establishments and miss the government operators entirely (§3) [3].

10. How to invest and the outlook

Public-market routes are exposure vehicles, not measures of the code. The only genuine listed pure-plays in the whole group are the independent MRO names in 48819 — StandardAero (NYSE: SARO), AAR (NYSE: AIR), and VSE (Nasdaq: VSEC) — plus diversified handling/services exposure through ABM (NYSE: ABM), SATS (SGX: S58), Agility Global (ADX: AGILITY), and General Dynamics (NYSE: GD). For 48811, there is no operator pure-play at all: reach the airport side through foreign airport equities (e.g., ASUR, NYSE: ASR) or a terminal sponsor (Ferrovial, Nasdaq: FER), and the ATC-modernization side through federal systems contractors (RTX, NYSE: RTX; Leidos, NYSE: LDOS). In every one of these names, U.S. air-transport-support work is a minority segment — the diligence question is how much revenue is genuinely tied to it [4][5][11].

Private and fixed-income routes are where U.S. exposure actually lives.

• Municipal airport revenue bonds — the large, liquid, retail-accessible way to lend to U.S. airports, backed by ring-fenced revenue; underwrite the specific airport's passenger trends, airline agreements, and debt-service coverage [16].
• Private-equity / infrastructure funds (Blackstone, KKR, Apollo, GIP/BlackRock, Carlyle) own the FBOs, terminals, ground handling, and — on the 48819 side — MRO platforms; stress downside passenger and flight-activity scenarios, minimum-revenue protections, construction and refinancing terms, and single-customer concentration [4][5][9].
• Direct small-business ownership — a single certificated repair station or FBO is a real path given 48819's fragmented tail [5].

Outlook (forward-looking judgments, not guarantees). The two children point the same direction for different reasons. 48819 rides a record in-service fleet flying older because of OEM delivery delays, a multi-year engine shop-visit wave, record air cargo, permanently elevated private-jet activity, and continued airline outsourcing — a favorable structural setup, best captured through listed MRO and PE-owned FBO/handling platforms [5][14]. 48811 rides a record airport capital cycle (~$28B/year against ~$174B of five-year needs) and a $12.5B ATC-modernization down payment with a chronic controller shortage behind it — a defensive, infrastructure-flavored setup where U.S. investors mostly participate through debt and private funds, plus the systems contractors [4][8][13]. The base case for the group is a well-funded, policy-driven infrastructure decade sitting on a public backbone you can't buy, with a fragmented private layer consolidating around scarce local access and technical capability. The classic mistake is treating traffic growth as sufficient: contract structure, leverage, labor scarcity, OEM competition, single-customer risk, and the durability of federal funding decide how much of that growth becomes investor cash flow — and those levers sit in different places in each child, so underwrite the two halves separately.

---

Sources

1. U.S. Census Bureau, "2022 NAICS Manual / Definitions — 4881 Support Activities for Air Transportation, 48811 Airport Operations, 48819/488190 Other Support Activities for Air Transportation" (definitions, illustrative examples, cross-references to 336411, 424720, 481). https://www.census.gov/naics/
2. U.S. Census Bureau, 2022 Economic Census — Concentration by Largest Firms, NAICS 4881 (receipts $38,175,672K; 4,565 firms; CR4 11.3%, CR8 19.8%, CR20 35.3%, CR50 52.4%; HHI 82.5). [Histometrics ground-truth dataset, stats-4881] https://www.census.gov/programs-surveys/economic-census/data/tables.html
3. U.S. Census Bureau, County Business Patterns 2023 — NAICS 4881 (establishments 6,822; employment 245,625; annual payroll $13,052,446K; Q1 payroll $3,199,198K) and CBP methodology on government/nonemployer/self-employed exclusions. [Histometrics ground-truth dataset, stats-4881] https://www.census.gov/data/datasets/2023/econ/cbp/2023-cbp.html
4. Histometrics child-industry primer 48811 — Airport Operations (rollup of 488111 Air Traffic Control and 488119 Other Airport Operations): receipts ~$14.47B, 142,448 employees, 2,585 establishments; CR4 25.7%, HHI 240.5; contract-tower oligopoly CR4 ~86%; government ownership of airports and the FAA; FBO/handling/concessions/terminal-P3 layers; PFC/AIP/Grant Assurances/Part 139; ATC modernization; listed proxies GD, FER, ASR, RTX, LDOS; muni airport revenue bonds. [Histometrics primer-48811]
5. Histometrics child-industry primer 48819 / 488190 — Other Support Activities for Air Transportation: receipts ~$23.7B, 103,177 employees, 4,237 establishments; CR4 15.4%, HHI 115; independent MRO, ground/ramp handling, FBOs, de-icing/testing/ferrying; unit economics and KPIs; Part 145/A&P/TSA/OSHA/EPA regulation; OEM-encroachment threat; listed names SARO, AIR, VSEC, ABM, S58, AGILITY, GD; PE-owned FBO and handling platforms. [Histometrics primer-48819 / primer-488190]
6. Federal Aviation Administration, "Airport Investment Partnership Program" — U.S. airports overwhelmingly owned by state/local governments and public authorities; full privatization capped and lightly used. https://www.faa.gov/airports/airport_compliance/privatization
7. Federal Aviation Administration, "FAA Contract Tower Program" — contract towers as ~half of federal towers, benefit-cost ≥ 1.0 requirement, same-standard staffing, cost-vs-FAA-staffed comparison. https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/mission_support/faa_contract_tower_program
8. Airports Council International–North America — economic-impact and infrastructure-needs studies and traffic reports (~$1.8 trillion footprint; ~$28B FY2025 capital spending; ~$173.9B five-year needs; 2025 North American traffic −0.7%). https://airportscouncil.org/intelligence/airport-infrastructure-needs-study/
9. FBO take-private and roll-up transactions — Signature Aviation (Blackstone/GIP/Cascade, ~$4.7B); Atlantic Aviation (KKR, reported ~$10B sale process to Apollo); Modern Aviation (Apollo/Tiger Infrastructure). [via Histometrics primer-48811 and primer-48819] https://www.blackstone.com/news/press/; https://www.bloomberg.com/news/articles/2025-04-16/kkr-is-said-to-explore-10-billion-sale-of-atlantic-aviation
10. Market Research Future, "US Aircraft Maintenance, Repair and Overhaul (MRO) Market" (~$51.69 billion, 2024) — broader total that includes in-house airline and OEM factory work excluded from NAICS 48819. https://www.marketresearchfuture.com/reports/us-aircraft-maintenance-repair-and-overhaul-market-21422
11. Listed independent MRO and services filings — StandardAero (NYSE: SARO), AAR Corp. (NYSE: AIR), VSE Corp. (Nasdaq: VSEC), ABM Industries (NYSE: ABM), General Dynamics / Jet Aviation (NYSE: GD). [via Histometrics primer-48819] https://ir.standardaero.com/; https://stockanalysis.com/stocks/air/; https://ir.vsecorp.com/sec-filings
12. Ground-handling consolidation — SATS Ltd. completes acquisition of Worldwide Flight Services (~€2.25B, 2023); Menzies Aviation acquires G2 Secure Staff (~$305M, 2025). https://www.sats.com.sg/investors/sats-wfs-acquisition/; https://menziesaviation.com/news/menzies-aviation-doubles-u-s-footprint-with-completion-of-305m-acquisition-of-g2/
13. Federal Aviation Administration, "Brand New Air Traffic Control System Fact Sheet" (2025) — $12.5B initial, ~$20B further need; related NextGen and facility-modernization background. https://www.faa.gov/newsroom/brand-new-air-traffic-control-system-bnatcs-fact-sheet
14. WingX / Private Jet Card Comparisons, "WingX 2025 Full-Year Private Jet Flight Activity Analysis" (U.S. ~2.63M departures, +5% YoY, +29% vs 2019). https://privatejetcardcomparisons.com/2026/01/08/wingx-2025-full-year-private-jet-flight-activity-analysis/
15. Aviation-support regulation — FAA 14 CFR Part 145 repair stations and A&P certification, TSA worker-access rules (49 CFR Part 1542), OSHA airline-industry hazards, EPA airport-deicing effluent guidelines, and local airport minimum standards. https://www.ecfr.gov/current/title-14/chapter-I/subchapter-H/part-145; https://www.epa.gov/eg/airport-deicing-effluent-guidelines
16. Federal Aviation Administration and municipal-market practice — Grant Assurances 24–25 (self-sustaining rates; airport-revenue anti-diversion), Passenger Facility Charge program ($4.50 cap, 14 CFR Part 158), Airport Improvement Program, Part 139 certification; general airport revenue bonds (GARBs) as the retail-accessible debt route. https://www.faa.gov/airports/aip/grant_assurances; https://www.faa.gov/airports/pfc