Airline Ancillary Revenue: Structure, Scale, and Implications for Airport Finance

What Ancillary Revenue Includes

Airline ancillary revenue encompasses all income generated from sources beyond the base passenger fare. The category includes a la carte services paid directly by passengers (baggage fees, seat selection, onboard food and Wi-Fi), commissions earned from third-party travel products (hotel bookings, car rentals, travel insurance), and — the largest component for U.S. network carriers — revenue from the sale of frequent flyer miles to co-branded credit card partners.^[1][2]

IdeaWorksCompany and CarTrawler projected global airline ancillary revenue at $148.4 billion for 2024, a 26% increase over the $117.9 billion recorded for 2023 and above the pre-pandemic record of $109.5 billion in 2019. For 2025, IdeaWorksCompany projected $157 billion in global ancillary revenue.^[2][3]

Ancillary revenue contributed 14.9% of total airline revenue globally in 2024. IdeaWorksCompany projects that share at 15.7% for 2025, up from 9.1% in 2016. The range across individual carriers spans from 3.2% for certain full-service airlines to 62% for Frontier Airlines.^[3][4][1][2]

The Largest Ancillary Revenue Generators

The IdeaWorksCompany 2025 Yearbook of Ancillary Revenue, covering 61 airlines' 2024 financial disclosures, ranks the top three carriers by total ancillary revenue as United Airlines ($10.6 billion, 18.6% of total revenue), Delta Air Lines ($10.2 billion, 16.8%), and American Airlines ($9.2 billion, 17%).^[4][1]

Among carriers where ancillary revenue exceeds half of total revenue, five airlines crossed the 50% threshold in 2024:^[1]

On a per-passenger basis, the leaders are Norse Atlantic Airways ($100.40), Jet2.com ($89.99), and Breeze Airways ($89.82). The 2025 Yearbook found that across its 61-airline dataset, per-passenger ancillary revenue increased 2.5% while per-passenger fares declined 3.8% in 2024.^[5][4]

Baggage Fees: The Original Unbundled Service

American Airlines introduced the first checked bag fee among U.S. full-service carriers in June 2008 and reported approximately $278 million in baggage fee revenue that year. Thirteen U.S. carriers collectively earned $7.27 billion from checked baggage fees in 2024, up from $7.07 billion in 2023 and $5.76 billion in 2019, according to Bureau of Transportation Statistics (BTS) data. American, Delta, and United each exceeded $1 billion individually in 2024.^[6][1]

BTS data for Q3 2025 shows baggage fees at $2.0 billion, representing 3.1% of total operating revenue for all 23 scheduled U.S. passenger airlines — compared to 3.0% in Q3 2024. Fares accounted for 73.6% of total operating revenue in Q3 2025, down from 75.5% in Q3 2024.^[7]

Southwest Airlines, the last U.S. carrier to include free checked bags in all fares, announced in 2025 that it would begin charging $35 for the first checked bag — ending its "Bags Fly Free" policy after more than 50 years. Southwest projected the change would generate $1.5 billion per year in new revenue.^[6]

Seat Selection: Overtaking Baggage at Some Carriers

Seat selection fees carry minimal incremental cost relative to baggage handling (no ground labor, no fuel penalty, no equipment). United Airlines collected $1.3 billion from seat selection fees in 2023, exceeding its $1.2 billion in baggage fee revenue for the same period — the first time seat selection surpassed baggage at a U.S. carrier.^[1]

Loyalty Programs and Co-Branded Credit Cards

For U.S. network carriers, the sale of frequent flyer miles to co-branded credit card issuers represents the single largest component of ancillary revenue. In 2023, Delta Air Lines received $6.8 billion from American Express, American Airlines reported $5.2 billion from co-branded card and partnership revenues, and United Airlines reported $3.2 billion primarily from payments to its MileagePlus program.^[8]

The IdeaWorksCompany 2025 Yearbook reports 2024 loyalty program revenue for the top three U.S. carriers as Delta SkyMiles at $7.1 billion, American AAdvantage at $7.1 billion, and United MileagePlus at $6.2 billion. American Airlines reported loyalty revenues up 14% year-over-year in 2024, with AAdvantage members accounting for 75% of premium cabin revenue.^[9][4]

Tom Fitzgerald, airline analyst at TD Cowen, estimates the profit margin on the loyalty program component of ancillary revenue at approximately 50% — compared to industry-wide net margins in the high single digits in a strong year. U.S. airlines collectively receive approximately $25 billion per year from co-branded credit card programs.^[10][8]

Delta Air Lines has stated publicly that it factors co-branded credit card revenue into route planning decisions — indicating that flights which appear to underperform on a fare-revenue basis may remain viable when loyalty program economics are included.^[11]

The Fare Decline Offset

The IdeaWorksCompany analysis for the 2025 Yearbook shows that the average one-way domestic fare declined $112 over the decade from 2015 to 2024, falling from $270 to $158. Over the same period, per-passenger spending on ancillary services rose by $11, reaching $25 per person. Approximately 45% of travelers purchase only the base fare, while 55% pay for at least one add-on.^[5][1]

This shift illustrates the structural change in airline revenue composition: base fares account for a declining share while ancillary revenue — particularly loyalty program revenue and a la carte services — accounts for a growing share. BTS data for Q3 2025 shows fares at 73.6% of total U.S. airline operating revenue, down from 75.5% one year earlier.^[7]

Regulatory Status

The U.S. Department of Transportation finalized a rule in April 2024 requiring airlines to disclose ancillary fees — including baggage, seat assignment, and change fees — at the time of fare search. Airlines for America, IATA, and eight carriers challenged the rule in federal court.^[12][13]

In January 2025, a three-judge panel of the Fifth Circuit Court of Appeals found the DOT had authority to issue such rules but had failed to make a study available during the public comment period, creating a procedural violation under the Administrative Procedure Act. The full Fifth Circuit reheard the case in October 2025. In February 2026, the Fifth Circuit Court of Appeals concluded that the procedural violation "may have affected the agency's determinations about the Rule's content and scope," and the court vacated the rule in its entirety.^{[13][14][15][12]}

Implications for Airport Finance

Airline ancillary revenue interacts with airport financial structures through several channels:

Revenue Composition and Rate-Setting

Airport airline rate-setting methodologies — whether residual, compensatory, or hybrid — are based on the relationship between airline-related revenues and airport costs. Under a residual framework, non-airline revenues (concessions, parking, rental cars) offset airline cost centers. But the relevant question for airports is which airline revenues are captured in the rate base. BTS data shows fares declining from 75.5% to 73.6% of U.S. airline operating revenue in a single year (Q3 2024 to Q3 2025), while ancillary categories grow. Much of that ancillary growth — loyalty program revenue, seat selection, bundled products — flows through channels that are not reflected in published fare data used by many airports for rate calculations and air service development benchmarking.^[7]

Enplanement Sensitivity

Ancillary revenue strategies affect airline capacity decisions. A route where the fare yield appears marginal may remain in service if the airline's revenue optimization model incorporates loyalty program revenue, ancillary attach rates, and credit card acquisition value. Delta's stated practice of including co-brand revenue in route economics illustrates this dynamic. For airports relying on enplanement projections for bond credit analysis and financial forecasting, the implication is that airline route-level economics are less visible when a growing share of revenue is earned outside the fare.^[11]

Non-Aeronautical Revenue Parallels

Airports face a structural parallel to airlines in the shift toward non-core revenue. ACI World data for 2023 shows non-aeronautical revenue at $54 billion globally (36.7% of total airport revenues), with car parking at 24% and retail concessions at 21% in North America. Both airports and airlines are rebalancing their revenue mix away from their traditional core product — the fare and the landing fee, respectively — toward auxiliary commercial activities.^[16][17]

The "Unbundled Passenger" and Concession Spending

The shift toward basic economy fares with stripped-out amenities creates a traveler who may arrive at the airport without having purchased food, beverages, or comfort items as part of the ticket. That traveler may redirect spending to airport concessions. Conversely, as airlines expand onboard retail (in-flight catering reached $19.6 billion globally in 2024, and in-flight shopping $12.3 billion), airlines and airports are competing for the same discretionary passenger dollar. Airports may wish to evaluate how airline unbundling and onboard retail expansion affect terminal concession capture rates.^[1]

Loyalty-Driven Capacity Decisions

When credit card issuers pay U.S. airlines approximately $25 billion per year for miles, and when a single airline receives $7.1 billion from one card issuer (Delta/Amex, 2024), route planning incorporates financial inputs that do not appear in DOT Form 41 fare data. Airport air service development teams working with published O&D fare data may be observing an incomplete picture of the airline's actual revenue per enplanement at their facility.^[4][10]

The Measurement Gap

These are structural shifts in how airline revenue is generated and allocated. The data is sourced and current, and the trend lines point in a consistent direction: ancillary revenue's share of total airline revenue has grown from 9.1% in 2016 to 14.9% in 2024 to a projected 15.7% in 2025. Airport financial models built on fare-based metrics face a growing gap between what they measure and what airlines actually earn.^[2][3]

Changelog
2026-03-06 — Initial publication.