Are Budget Airlines Worth It? The Math After Spirit

• 2 May 2026

  The day Spirit stopped flying

• ~14%

  Fare rise on former Spirit routes within days

• ~2%

  Share of U.S. domestic capacity Spirit held

• $60–$99

  Frontier carry-on, depending on when you buy

For twenty years the argument about ultra low-cost carriers was theoretical: were they a genuine bargain or a bait-and-switch with a seat pitch problem? In May 2026 the largest one in America stopped flying, and the question got answered by the market within about a week.

What Spirit's collapse proved

Spirit ceased all operations on 2 May 2026 after running out of funding, the first shutdown of a major U.S. airline in roughly a quarter century. It had filed for Chapter 11 in November 2024, emerged, and filed again in August 2025; the second attempt did not produce a buyer or a rescue. Around 9,000 scheduled flights through the end of May were cancelled, roughly 1.8 million seats.

What happened next is the useful part. Prices on Spirit’s former routes rose about 14% on average within days. New York to Miami, one of the most heavily served leisure markets in the country, jumped 22% week over week. Analysts put the medium-term rise at 15% to 20% on routes no other low-cost carrier takes over, and Spirit’s historical exits from individual markets moved average fares around 23%.

A budget airline is unbundled, not cheap

The confusion at the heart of this question is that people compare a budget airline’s fare to a full-service airline’s fare, when the two numbers describe different products.

An ultra low-cost carrier sells transportation and nothing else. The fare buys a seat the airline assigns you and one personal item that fits under the seat in front — typically about 14 by 18 by 8 inches. Carry-on bags, checked bags, seat selection, priority boarding, changes and anything to drink are separate purchases, priced to be profitable rather than to be convenient.

This is not a trick. It is a legitimate model that produces genuinely cheap travel for people who need nothing else, and it fails for everybody who does. The mistake is not the airline’s pricing; it is comparing the advertised fare rather than the total.

The fees, and where they bite

The fee that catches people is the carry-on, because it is the one nobody expects to pay for and the one that escalates fastest as departure approaches.

Frontier, now the largest remaining ultra low-cost carrier, charges roughly $60 to $99 for a carry-on depending on when it is bought, with the gate the most expensive place to buy one. It also sells bundles that fold a carry-on, a checked bag, seat selection and boarding into a single price — around $69 for the mid-tier and $99 for the full one, per direction. Price the bundle against the individual add-ons before choosing; on a round trip with a bag it frequently wins, which tells you something about the individual prices.

Three trips, priced properly

Case 1: One night, backpack only

A $59 ULCC fare against a $118 main cabin fare on a full-service carrier. Nothing to add on either side. The budget airline wins by $59, and this is the trip the entire model was designed for. Take it.

Case 2: Four nights, one carry-on, aisle seat

The same $59 fare, plus roughly $70 for the carry-on each way and $20 for a seat each way, is about $239. The $118 main cabin fare includes both and comes to $118. The budget airline is now twice the price, on the same route, for a worse product.

Case 3: Family of four, one checked bag each, week-long trip

Multiply everything by four and the gap becomes the cost of a hotel night or two. This is the case where the totals almost always favor the full-service carrier, and where the per-person arithmetic that helps families on airport choice works against them on fees.

ULCC versus basic economy on a big airline

The genuinely close comparison is not ULCC versus main cabin. It is ULCC versus basic economy, and it is closer than either side admits.

Basic economy on American and Delta includes a full-size carry-on. A ULCC fare does not. So a basic economy ticket $30 more expensive than a budget fare is usually the cheaper ticket once a roller bag is involved, and it comes with a route flown six times a day rather than once. Where basic economy loses is the mile and elite-credit forfeiture and the inability to change — all of which is laid out in the basic economy arithmetic.

The cost that never appears on the fare

This is the cost nobody prices, and it is the one that turns a good fare into a ruined trip.

Ultra low-cost carriers run thin schedules — often one flight a day on a route — with high aircraft utilization and few spare aircraft. They also hold few or no interline agreements, meaning no other airline is contractually obliged to take you when their flight cancels. On a full-service carrier a cancellation is a rebooking two hours later. On a ULCC it can be a two-day wait or a walk-up fare on someone else.

What you are owed when it goes wrong

Federal rules do not care what you paid. Every point below applies to a $49 fare exactly as it applies to a $900 one.

• Cancellation refunds. If the airline cancels or significantly changes your flight and you decline what it offers, you are entitled to a refund to your original form of payment — not a voucher. The detail is in what you are owed when a flight is cancelled or delayed.
• The 24-hour rule. Bookings made at least seven days before departure can be cancelled free within a day of purchase.
• Bag fee refunds. Your checked bag fee comes back automatically if the bag is delayed beyond the federal thresholds — see what the airline owes you for a delayed bag.
• Denied boarding compensation. The federal formula applies on every carrier, covered in what you are owed if you are bumped.

Who should still fly them

Budget airlines are the right choice more often than their reputation suggests. Specifically:

• Hand-luggage travelers. If your trip fits in a backpack, no other airline can beat the total.
• Short trips with slack. A weekend where arriving a day late would be annoying rather than expensive.
• Underserved airports. Allegiant and Avelo fly routes from small cities that no full-service carrier serves nonstop, and the comparison there is against a connection plus a drive.
• Positioning flights. Getting to a gateway for a long-haul departure the night before, where the ticket is cheap and expendable.

They are the wrong choice for anyone flying to something that starts at a fixed time, anyone traveling with checked bags for a family, and anyone whose return flight is the last one of the day.

Who is left, and what happens to fares

Frontier is now the largest remaining ultra low-cost carrier, alongside Allegiant, Avelo and Breeze — each with a different network shape. Allegiant and Avelo concentrate on small airports the majors ignore; Breeze flies mid-size point-to-point routes. Southwest is a low-cost carrier rather than an ultra low-cost one, and since 2025 it charges for checked bags like everyone else.

None of them has Spirit’s scale, and meaningful expansion into its former routes takes time — aircraft, crews and slots do not move quickly. The practical consequence for the next year or two is that cheap domestic fares are less abundant and more time-limited than they were, which raises the value of watching rather than searching. The mechanism behind that is in how airlines actually price a seat.

The two-minute comparison

1. Add every fee you will actually pay to both fares. Carry-on, checked bag, seat. Double all three for a round trip.
2. Count the daily flights on the route. One a day against six a day is a real difference in what a cancellation costs you.
3. Ask what being a day late costs. If the answer is nothing, the budget fare is fine. If it is a cruise departure or a wedding, it is not.
4. Buy the extras at booking, not later. Every one of them is cheapest in the original transaction.
5. If the totals land within $50, take the bigger airline. You are buying the recovery options, and at that margin they are free.

None of which is an argument against budget airlines. It is an argument for pricing them honestly — and for noticing that the cheapest ticket and the cheapest trip are different things. The rest of the system is in the cheap flights playbook.