What Budget Airlines Don't Tell You: The Real Cost of That '$39 Flight' After All the Fees

There's a particular kind of frustration that hits when you click on a $49 flight deal, spend 15 minutes filling out your information, and arrive at the checkout page staring at a $147 total. It happens to almost everyone who books with a budget carrier, and it's not an accident — it's a business model.

Ultra-low-cost carriers (ULCCs) like Spirit, Frontier, and Allegiant built their entire operation around unbundling. The base fare covers one thing: your body in a seat. Everything else — your bag, your chosen seat, a printed boarding pass, even a cup of water on some airlines — costs extra. The question isn't whether fees exist. It's whether the final total is still a deal.

Let's pull back the curtain.

How the Unbundling Model Actually Works

Legacy carriers like Delta and American include a standard carry-on, seat assignment (at least in basic economy), and a complimentary non-alcoholic beverage in their base fare. Budget carriers strip all of that out and charge for each piece individually.

The logic from the airline's perspective is actually sound: travelers who pack light and don't care where they sit genuinely do pay less. The problem is that most travelers don't realize how many of those "optional" add-ons they'll end up needing until they're deep in the booking flow — and by then, they've already invested time and mental energy into the purchase.

Here's a breakdown of what the major US budget airlines typically charge for the most common add-ons.

Carry-On Bag Fees: The One That Gets People Every Time

This is where budget airlines make a significant chunk of their ancillary revenue, and it's the fee that surprises travelers most.

• Spirit Airlines: A carry-on bag (the kind that goes in the overhead bin) costs anywhere from $35 to $65 depending on when you add it. Add it at the gate? That's up to $100.
• Frontier Airlines: Similar structure — carry-on fees range from $30 to $60 online, with gate prices climbing higher.
• Allegiant Air: Carry-on fees typically run $10 to $75 depending on the route and timing.
• Southwest Airlines: Here's the outlier — Southwest still includes two free checked bags and a free carry-on. It's one of the main reasons their "higher" base fares often end up cheaper in total.

The practical implication: if you're traveling with a standard roller bag, add $40 to $60 to whatever base fare you're looking at on Spirit or Frontier before you even compare it to competitors.

Checked Baggage: It Adds Up Fast for Longer Trips

If you're heading somewhere for more than a long weekend, you're probably checking a bag. Budget airline checked bag fees generally run:

• Spirit: $35 to $65 per bag, per direction (so $70 to $130 round-trip for one bag)
• Frontier: $30 to $60 per bag, per direction
• Allegiant: $10 to $50 per bag depending on route

For context, Delta and American charge $30 for the first checked bag on most domestic routes — less than Spirit or Frontier if you're not a member of their loyalty programs or credit card holders.

Seat Selection: Paying to Not Sit in the Middle

Budget airlines assign you a seat for free — but it's random, and it's almost always a middle seat near the back. Want to sit next to your travel companion? That costs extra. Want an aisle seat? Extra. Extra legroom? Definitely extra.

• Spirit's Big Front Seat (their premium option up front) runs $12 to $150 depending on the route.
• Frontier's Stretch seating adds $15 to $45 per segment.
• Standard seat selection on either carrier typically runs $5 to $25 per seat, per leg.

For a family of four flying round-trip, seat selection alone could add $80 to $200 to the total bill.

The Fees You Might Not Expect

Beyond bags and seats, here's where things get genuinely surprising:

• Printing your boarding pass at the airport: Spirit charges up to $25 if you don't check in online and print at home. Yes, really.
• Booking fees: Frontier charges a service fee for bookings made over the phone. Spirit's website booking fee is built into the fare, but third-party bookings can trigger additional charges.
• Snacks and drinks: Budget carriers generally charge for everything on board, including soft drinks. Budget $5 to $15 if you want anything during the flight.
• Travel insurance and seat upgrade upsells: These get pre-checked during checkout on some platforms. Always scroll carefully before confirming.

The Real-World Cost Comparison: A Sample Route

Let's use a concrete example: a round-trip flight from Chicago O'Hare (ORD) to Orlando (MCO) for one traveler with a carry-on bag who wants an aisle seat.

Southwest wins that round — and it's not even close. The "cheapest" Spirit fare ends up being one of the pricier options once you add what most travelers actually need.

Note: Prices vary significantly by route, timing, and booking window. Always run the full calculation before assuming the lowest base fare is the best deal.

Your Pre-Booking Checklist

Before you finalize any budget airline ticket, run through this quick mental checklist:

• Do I need a carry-on bag? (Add $40–$65 if yes)
• Am I checking a bag? (Add $35–$65 per direction if yes)
• Do I need a specific seat or to sit with someone? (Add $10–$30 per person per leg)
• Will I want food or drinks on the flight? (Budget $5–$15)
• Am I booking online directly to avoid phone/service fees?
• Are any add-ons pre-checked in the booking flow that I need to remove?
• What's the total — and how does it compare to Southwest, JetBlue, or a legacy carrier on the same route?

So Are Budget Airlines Ever Actually Worth It?

Absolutely — under the right circumstances. If you're traveling with just a personal item (think: a small backpack that fits under the seat), don't care where you sit, and are flying a route where the budget carrier is the only affordable option, the savings can be real and meaningful.

But for anyone checking a bag or traveling with family, the math often favors Southwest, JetBlue, or even a basic economy fare on a legacy carrier. The key is doing the full calculation — not just clicking the lowest number on the search results page.

At FreeFlights, we're all about helping you find the deal that's actually a deal. Sometimes that's Spirit. Sometimes it's Delta. The only way to know is to add up every single line before you hit "buy."