Did You Just Pay Extra to Book a Flight Online? The Secret Fee to Watch Out For

If you've booked a flight on low-cost airline Breeze Airways, you may notice a perplexing additional charge when you check your ticket. It recently took one traveler by surprise.

This "technology development charge" may seem suspicious, but it's much more common than you might think. It's a fee that the airline tacks on to your flight ticket to pay for the technology service you used while purchasing the ticket. Basically, you're being charged for using the airline's website.

Breeze isn't the only airline to do this. Several U.S.-based low-cost airlines, like Frontier, Allegiant, and Spirit, all charge extra fees for booking your ticket online—and even for booking your ticket over the phone. While these airlines all offer low base fares, a $27 technology fee incurred on each leg of your trip could make a difference when you're trying to fly for less.

So why does a fee like this exist? In the U.S., all domestic airfares are subject to a 7.5 percent excise tax, a tax specifically for goods and services. Any fee, from a checked bag to a seat assignment, avoids this tax. Calling part of the cost of your ticket a "technology fee" saves the airline taxes on that part of your ticket.

If you're thinking of getting out of it, think again. The Department of Transportation requires that all fees must be optional. Technology fees are optional because customers can avoid them by purchasing their ticket without using technology—by buying their ticket at the airport.

If you really want to avoid this fee, it may require hopping in the car the next time you plan a trip. While a dedicated trip to the airport to purchase a flight is not recommended, if you're already at the airport and know you need to book a ticket for an upcoming trip, it can be worth stopping by the counter of your low-cost airline of choice.

Just don't think the airlines will make it easy on you. Breeze Airways, for example, only allows in-person purchases at its ticket counter on Tuesdays from 11 a.m. to 1 p.m.

It benefits airlines to make purchasing your ticket at its airport counter as tricky as possible since it costs more money for the airline to process your ticket in person. So block off your lunch hour: saving money on your next vacation may involve some extra strategy.