Okay so this started because I booked a $41 flight from Orlando to Hartford and then paid $89 in fees before I even reached the gate.
I sat there in the terminal, staring at my receipt, doing the kind of math you do when you've clearly been outsmarted by a pricing algorithm. $41 became $130. The "budget" airline had gently, politely relieved me of an extra ninety bucks. And the wild part? I still came out ahead of the legacy carrier by about $60.
Which made me ask the question that ate the next three weeks of my life: how are these fares even possible?
I now know more about aircraft seat pitch and ancillary revenue than any human should. My partner walked in at one point and I had four airline investor presentations open and a spreadsheet titled "WHY SPIRIT." He did not ask questions. He has learned.
So here's what I found. All of it. Grab coffee.
First, the thing nobody tells you: there are two completely different airline business models
Here's the thing. When we say "airline," we're actually talking about two species of animal that happen to look similar from the outside.
There are legacy carriers (Delta, American, United). And there are ultra low cost carriers, which the industry calls ULCCs, and which the rest of us call "the ones where you pay for the carry-on." Spirit, Frontier, Avelo, and to a softer degree Breeze all live in this second camp.
They are not the same business wearing different paint. They make money in fundamentally different ways.
A legacy carrier sells you a bundle: seat, bag, snack, loyalty points, a lounge you'll never use, and the vague promise of an upgrade. A ULCC sells you a seat. Just the seat. Everything else is a separate transaction, and that unbundling is the entire trick.
Right?
Once I understood that, the $39 fare stopped looking like magic and started looking like a very deliberate machine.
Where the money actually comes from (it's not the ticket)
Let me back up for a second, because this is the part that reframes everything.
On a legacy carrier, most revenue comes from the fare itself, plus a serious chunk from business travelers and premium cabins. On a ULCC, the base fare is often close to their actual cost of flying you. The profit lives somewhere else entirely.
That somewhere else is called ancillary revenue. Fancy term for "everything that isn't the ticket."
- Bag fees (the big one)
- Seat selection fees (yes, to choose the seat you already bought)
- Priority boarding
- Change and cancel fees
- That $3 for a soda
- Booking through the app instead of a "convenience fee" for the website (I wish I were joking)
For the ULCCs, ancillary revenue can be roughly 40% to 55% of total revenue. Read that again. Almost half the money doesn't come from selling you a flight. It comes from selling you the flight's accessories.
So when Frontier advertises a $19 fare, they are not being charitable. They're using the lowest possible number as bait to get you into a funnel where the average person adds $60 to $90 of stuff. And it works, because the $19 got your attention and now you're already emotionally committed to the trip.
That's not a scam, by the way. It's just a different deal. You're paying for exactly what you use. The problem is that most of us are bad at predicting what we'll use.
The five levers that make the base fare so low
I kept looking for one trick. There isn't one. There are five, and they stack.
Lever one: they cram in more seats. A ULCC Airbus A320 might have 186 seats where a legacy carrier flies the same plane with 150. Thinner seats, less legroom (that's the 28-inch pitch your knees warned you about), no seatback screens because screens are heavy and heavy costs fuel. More seats means the cost of the flight is split across more people. Your slice gets cheaper.
Lever two: they fly the plane constantly. An idle plane earns nothing and costs a fortune. ULCCs run brutal aircraft utilization, sometimes 12+ hours a day in the air, with fast turnarounds. That $100 million jet has to hustle. The more hours it flies, the lower the cost per seat.
Lever three: one type of plane. Spirit and Frontier basically fly one aircraft family. One type means one set of spare parts, one training program for pilots and mechanics, one maintenance playbook. Southwest built an empire on this with the 737. Simplicity is cheap.
Lever four: they use cheaper airports and point-to-point routes. Instead of running everything through an expensive mega-hub, ULCCs often fly point to point, sometimes into secondary airports with lower fees. This is why Avelo and Breeze love the airports the big guys ignore. Lower airport costs, less connecting complexity.
Lever five: skeleton service. No lounges. Tiny corporate staff. No fancy loyalty program to fund. Pay for your own water. Every cost the legacy carriers absorb into the ticket, the ULCCs either cut or charge for separately.
Stack all five and you get a genuinely lower cost to fly a person from A to B. The low fare isn't fake. It's engineered.
Yeah. That last part is the piece that changed how I look at a fare.
A field guide to the budget carriers (they are NOT interchangeable)
Okay so I cannot let you leave thinking Spirit and Breeze are the same thing, because they are wildly different animals and I have named them accordingly.
The Purist (Spirit, Frontier): The classic ULCC. Rock-bottom base fare, everything unbundled, fees for days. Perfect if you travel light and read the fine print. Punishing if you don't.
The Newcomer (Avelo): Point-to-point specialist that flies routes nobody else does, often out of smaller airports. The value isn't just price, it's the nonstop that used to be a two-connection nightmare.
The Hybrid (Breeze): This is where it gets interesting. Breeze looks like a ULCC (unbundled, underserved routes) but acts a little like a nice airline (extra legroom options, no change fees on some fares, actual customer service energy). It's a ULCC that went to therapy.
The Legacy-That-Acts-Budget (Southwest, kind of): Not a true ULCC, but it built its whole thing on the single-fleet, fast-turn, point-to-point model. And famously, two free checked bags, though the ground under that has been shifting lately. Different species, borrowed some genes.
Knowing which animal you're dealing with is the difference between a great deal and a receipt that makes you sad in a terminal.
When the cheap fare is secretly the expensive one (the actual math)
Here's what's wild: the budget fare and the "real" fare often converge, and sometimes the budget fare wins the race to the bottom of your wallet.
Let me show you the math that lives in my spreadsheet. Say you're flying round trip and you're a normal human with a normal amount of stuff.
- Base ULCC fare: $78 round trip (great, love that)
- Carry-on bag, both ways: +$60 (yes, the carry-on, not the checked bag, the carry-on)
- Seat selection so you and your travel partner sit together: +$32
- Priority boarding because otherwise your bag gets gate-checked: +$20
- One snack and a coffee because you're a person: +$12
That $78 fare is now $202. And the legacy carrier's fare, which included the carry-on and seat selection, was $215. You saved thirteen dollars and gave up legroom and a seatback screen to do it.
Now run the SAME comparison as a person traveling with a backpack that fits under the seat, who doesn't care where they sit, who brings their own water and a granola bar. That person pays $78. Full stop. They just beat the legacy fare by $137 and honestly they're the smartest one in the airport.
So the answer to "is the budget airline actually cheaper" is the most annoying answer in travel: it depends entirely on you.
The types of traveler, ranked by how much ULCCs love them
I built a taxonomy. I couldn't help it.
- The Underpacker (ULCCs adore this person): personal item only, no seat preference, no snacks. Pays the base fare and walks away a winner.
- The Realist (comes out roughly even): one carry-on, wants a seat, will buy a coffee. Ends up near the legacy price and picks based on schedule.
- The Optimist (ULCCs feast on this person): "I'll just add the bag at the airport." The airport bag fee is the most expensive bag fee. It is designed to punish the optimist. Do not be the optimist.
- The Denier (should not be here): three bags, a stroller, wants to change the flight twice. This person should book a legacy carrier and will be much happier and possibly richer.
I have been all four of these people. The Optimist cost me the most. The airport bag fee is a tax on hope.
So how do you actually win at this?
Here's the thing: you don't beat the ULCC model by avoiding it. You beat it by using it exactly as designed.
1. Add every bag online, in advance, never at the airport. The gap between an online bag fee and an airport bag fee is genuinely insulting. 2. Measure your bag before you go. ULCC gate agents get commission-style incentives on catching oversized bags at some carriers. That "personal item" sizer is not decorative. 3. Do the all-in math before you book. Add the base fare plus every fee you'll actually incur, THEN compare to the legacy price. The base fare is a headline, not a total. 4. Travel light on purpose. This is the single biggest lever you control. A person who fits everything in a personal item is essentially immune to the entire fee structure. 5. Save the ULCC for short hops. Two hours in a thin seat is fine. Five hours in a thin seat with no screen and no legroom is a decision you'll regret somewhere over Kansas. 6. Skip the change fees by being sure of your dates, because on a true ULCC the change fee can cost more than the ticket.
Do that and the model flips in your favor. You get the engineered-low fare without funding the ancillary machine.
The bigger thing I didn't expect to find
Okay, I'll get a little earnest for one second (bear with me).
The rise of ULCCs is genuinely the reason a normal person in Florida or Texas can fly somewhere on a whim for the price of a nice dinner. That competition drags down fares across ALL airlines, even the legacy ones, on any route where a Spirit or a Frontier shows up. The budget carrier in your market is quietly saving you money even on the flights you book with someone else.
So I went in cynical and came out weirdly grateful. The $39 fare is real. It's just a door into a store, and the store is optional if you know where the exits are.
The travelers who lose at this game are the ones who think the base fare is the whole price. The travelers who win are the ones who read the menu, order only what they want, and walk out with a genuinely cheap flight and their dignity intact.
Be the second kind. And measure your carry-on.
The bottom line
Budget airlines are cheap because they engineered a lower cost to fly you and moved the profit into fees you can mostly avoid. The fare is honest. The total is up to you.
Before you book any budget fare, do the all-in math and compare it to the full-service price with the bag and seat included. Sometimes the ULCC wins by a hundred dollars. Sometimes it loses by thirteen. The only way to know is to add it up.
If doing airfare math for fun sounds exhausting (fair), that's genuinely our job. We watch fares across the budget carriers and the legacy carriers from all 8 of our airports and flag the ones that are actually a deal after the fees. For more on the mechanics, read Noah's complete guide to finding cheap flights, and if you want the honest take on comfort versus price, browse more in Airlines & News. Then sign up for Early Bird Air free, and let Premium Plus do the all-in math for you.