While I largely avoid ULCCs like Frontier Airlines and Spirit Airlines these days due to their worsening value and customer experience, there are times when the price is too good to pass up.

However, I see people forking over hundreds of dollars for luggage, seats, snacks, and other add-ons every time because they ignored or misunderstood the a-la-carte business model.

The recent controversy involving Frontier reportedly charging people for bags within the size limits and then taking a commission has not helped the confusion.

Research the no-frills rules before you show up to the airport

The a-la-carte rules of ULCCs are relatively simple: the base fare gets you an unassigned seat and a personal item, but everything else — including even a cup of water — costs extra.

This means parties will only be guaranteed to sit together if they pay for each seat, and I recommend bringing your own snacks and drinks if you don't want to pay for the overpriced options on board.

But I think what surprises new flyers the most is how strict the bag size and weight limits are.

My backpack fits perfectly inside the personal item size checker on both Frontier and Spirit.



Taylor Rains/Business Insider

Frontier and Spirit require personal items to be 18 x 14 x 8 inches or smaller and don't allow checked bags bigger than 62 linear inches.

One important detail: Frontier's checked bag weight limit is 40 pounds compared to Spirit's 50 pounds — something I've seen trip people up when the ping-pong between the two carriers.

Further, the carry-on bag restrictions vary slightly at 24 x 16 x 10 inches and 22 x 18 x 10 inches, respectively. These rules are found on the airline's websites, and the same goes for other global ULCCs like Ryanair and Allegiant Air.

The rules may be annoying, but luggage is a lucrative ancillary revenue stream for the company. In 2023, global airlines raked in some $33 billion in bag revenue alone.

If you inadvertently show up at the airport with luggage that is too big or heavy, I recommend downsizing if you have time or taking the loss because gate agents are required to charge you — and arguing likely won't change their minds.

Always book directly through the airline

Frontier and Spirit allow customers to book flights on third-party websites like Priceline or Booking.com. While the base fare is sometimes cheaper, I'd recommend against this.

These websites don't always let you add bags at booking, possibly misleading travelers into thinking some luggage is included. Plus, some charge an extra fee to charge for a bag.

For example, an early August flight on Spirit from New York City to Orlando on Spirit can be purchased on Priceline for the same price as the airline website, but each added bag charges a $7 "convenience fee."

A screenshot of the Priceline page showing a $7 convenience fee and a total price of $264 with a checked bag.



Priceline.com

You could add bags to your reservation after booking, but — because of the way Spirit is set up — will cost more than if you did it at booking on its website.

Another third-party website called "TravelGo" offers the same ticket for about $10 cheaper but describes the carry-on allowance as "subject to airlines" for all fares. I can imagine how inexperienced flyers trying to save a few extra dollars could get confused and show up with an unpaid carry-on.

A screenshot of TravelGo's website showing the carry-on allowance as "subject to airlines."



TravelGo

In my experience, the process is much clearer when booking direct, thanks to the clear messages about bags, seats, and other add-ons costing extra unless you "bundle."

If you're unsure, call the airline — but don't let them make the reservation for you. That also costs extra.

Do the math before you book a ULCC

I only pay for an extra bag or a seat when absolutely necessary on a ULCC. However, once you add everything, booking a mainline carrier like American, Delta, or United is sometimes cheaper.

In a previous article, I used the NYC to Orlando example to illustrate how the fees can add up on a ULCC, and I've found the same results on several other routes I've researched.

For instance, a roundtrip flight between Denver and Seattle in August costs $187 for basic economy on United and $267 on Delta.

Once you click on the return options, the Delta flight costs $267 roundtrip, not $228.



Google Flights

United's includes a random seat and a personal item. Paying $60 more for regular coach adds a carry-on and a seat selection. Delta's basic fare already includes a carry-on but no pre-assigned seat, but paying up for regular economy with a seat would cost $347.

The base fare for the same route on Frontier with similar departure times on both legs is $197. Once you add the cheapest seat for $39 each way and a carry-on bag for $69 each way, the total price is $413.

The fees on Frontier add up once you start paying for both directions.



Frontier Airlines

Another example I found is between Las Vegas and Chicago, with Spirit costing more than American after adding bags.

Just because it's low cost doesn't mean it's actually the lowest price anymore. Plus, ULCCs will not provide you with a better flight experience due to their no-frills planes and poor customer service and reliability.

Don't bank on TikTok 'hacks'

Frequent flyers and TikTok users have been testing the limits of ULCC rules for years, and many have found ways to bypass the size and weight rules and carry more than their ticket allows.

Some have shown up to the airport wearing everything that couldn't fit in their personal item — think that episode of Joey from the TV show Friends — while others have stuffed extra needs into a pillowcase.

A Business Insider reporter even tested a viral hack in August 2023, in which people stuffed extra items into the pockets of a fishing vest and wore it for the flight.

The fishing vest could fit the BI reporter's laptop in the back pocket.



Hannah Towey/Business Insider

The vest hack worked for our reporter, and I've seen the pillow trick be successful — but these strategies are risky and could cost you hundreds in unexpected fees if you get caught.

A Frontier gate agent in Orlando recently stopped a Buffalo-bound passenger from bringing a pillowcase full of items, as shown in a viral TikTok video posted on June 4.

Spirit's own website says neck and head pillows can be carried if they fit into your personal item — but one stuffed to the brim with extra clothes could end in you shelling out more money in a carry-on fee than the price of the flight itself.