The Hidden Cost of Flying: Ancillary Fees by Airline, 2023–2025

Airline ticket prices are a polite fiction. The number you see on Skyscanner or Google Flights is the starting point of a negotiation the airline has already won — they know what you'll end up paying, and they've engineered the experience accordingly.

Using U.S. Department of Transportation financial data (Form 41 Schedule P-1.2) combined with T-100 traffic statistics, we tracked baggage fees, cancellation fees, and total ancillary revenue per passenger for ten major U.S. carriers across 2023, 2024, and 2025. The findings reframe how you should think about cheap flights.

The gap between the cheapest and most expensive is stark: Frontier charges $22.48 per passenger in bag fees while Delta charges $5.71 — nearly four times less. Southwest, which ran its "Bags Fly Free" policy for over five decades as a core brand promise, finally dropped it in May 2025 — and now sits at $3.46/pax for their first partial year of fees.

The Full Picture: Add Cancellation Fees

Bag fees are only part of the story. Cancellation and change fees add another layer — and the distribution is surprising.

Alaska's cancellation fees stand out. At $5.31 per passenger, they're collecting more in change/cancellation revenue per head than United, American, or Delta — despite being a smaller carrier. Their $17.32 total ancillary per passenger is the highest outside the pure ULCC segment.

The big three surprise: American ($9.18), United ($9.31), and Delta ($6.43) are far cheaper in total ancillary fees per passenger than the budget carriers. If you're choosing between a $180 American fare with no bag fees and a $140 Frontier fare with $28 in ancillary fees, the math is closer than it looks.

Three-Year Trends: Winners and Losers

The End of "Bags Fly Free"

For over fifty years, Southwest Airlines built a brand identity around one simple promise: Bags Fly Free. No first bag fee. No second bag fee. It was a genuine competitive differentiator — and a direct attack on the legacy carriers who charged $25–$35 per bag. In May 2025, Southwest ended it. The data tells you just how significant that decision was.

In 2023, Southwest's bag fee revenue was $71M — almost entirely from oversize and overweight charges, since standard bags were free. In 2025, after ending "Bags Fly Free," they collected $569M. That's nearly half a billion dollars in new revenue created by a single policy decision. And they did it while carrying fewer passengers than 2024 (164.3M vs 171.1M) — meaning the brand promise was already eroding before the policy changed. Whether the revenue fully compensates for the loyalty cost will only become clear in 2026 and beyond.

Frontier's Declining Grip

The opposite trend is playing out at Frontier. As the ULCC most dependent on bag fees (20% of total revenue), Frontier has seen per-passenger bag revenue fall steadily: $29.37 in 2023 → $25.90 in 2024 → $22.48 in 2025. That's a 23% drop in three years.

Frontier carried almost the same number of passengers in 2025 as in 2024 (31.7M vs 31.5M), but extracted significantly less per head. The pressure likely comes from multiple directions: post-Spirit competition for ULCC passengers, growing savviness among budget travelers comparison-shopping total costs, and increasing competition from Southwest's new fee structure occupying the same price tier.

What This Means When You Book

A few rules of thumb from the data:

• Delta is the most fee-efficient major carrier at $6.43 total ancillary per passenger — and they eliminated change fees permanently. For a traveler checking one bag and valuing flexibility, Delta's headline fare is often the real price.
• Frontier and Allegiant add $27–28 per passenger in fees on top of base fares. On a round trip, that's $54–56 per person before you've even thought about seat selection.
• Alaska's cancellation fees deserve attention — $5.31/pax is high for a carrier that markets itself as traveler-friendly. Check their fare rules before booking.
• Southwest's "Bags Fly Free" era is over. Their $3.46/pax in 2025 reflects only 8 months of fees — expect 2026 to land closer to $5–6/pax for a full year. Factor that into your fare comparisons.
• United and American are the best value among legacies for bag fee per passenger — both under $8.50, similar pricing despite very different network strategies.

The Bottom Line

The airline industry has perfected the art of making cheap look cheap until you're at the gate. The data across three years tells a consistent story: the carriers with the highest base fares tend to charge the least in ancillary fees per passenger, while the carriers with the lowest advertised fares extract the most through fees. The gap between a $22 Frontier ticket and a $150 Delta ticket is almost always smaller than the prices suggest.

The smartest booking decision is the one that adds up the total — fare plus likely bag fees plus cancellation policy — before clicking purchase.