10 Airlines That Charge the Most Hidden Fees, New Data Shows

Booking travel is stressful in general, between ensuring that you have the right dates and times scheduled, rides to and from the airport, and hotels booked. Combine that with the fact that you're also searching for the best deal on airfare, and things get that much more complicated. It's no big secret that airlines often tack on some hidden fees for different amenities, which can add up quickly and leave you wondering why your once-affordable base fare is no more.

Now, NetVoucherCodes—a website aimed at helping you save while shopping online—conducted a study to find out which carriers are the worst offenders when it comes to these miscellaneous charges. To do so, the site selected a sample "short-haul" flight for each airline that had the same date, similar flight route, and similar number of miles traveled. Researchers then went through the booking process to find hidden fees (defined as optional add-ons that aren't required to fly but may make you more comfortable), including the cost of seat selection, carry-on bags, checked bags, flight insurance, and onboard WiFi.

Interested to see which U.S. airlines might end up costing you more than expected? Read on to find out the 10 carriers that charge the most hidden fees, according to data.

RELATED: JetBlue Is Cutting Flights to 6 Major Cities, Starting Oct. 28.

Hawaiian Airlines came in at number 10 in terms of hidden fees. For a $54 flight, there were $38 in additional charges, per NetVoucherCodes' research, and when added to the total purchase, the flight was 7o percent more expensive.

Hawaiian charged $25 for a checked bag—which was the lowest of the other nine U.S. airlines on this list—and $13 for insurance. WiFi, a carry-on bag, and seat selection were all included with the base fare.

RELATED: Travelers Are Boycotting Southwest Over New Boarding Change.

Coming in at number nine is American Airlines, which averaged $52 in hidden costs for a $55 flight, making it 95 percent more expensive, per NetVoucherCodes' data.

A free checked bag is essentially unheard of these days, but American was on the lower end, charging $30—and they gave a carry-on for free. Seat selection averaged about $12, and WiFi was another $10.

RELATED: American Is Cutting Flights to 5 Major Cities, Starting Oct. 29.

Behind American was Alaska Airlines, which also gave a free carry-on and charged the same $30 for a checked bag.

Alaska's seat selection was a little pricier, coming in a $20, but WiFi was a bit cheaper, at $8. In total, the airline charged roughly $58 in hidden costs for a $55 flight, upping the total cost by 105 percent.

The budget airline Allegiant Air claimed the number seven spot. For the flight selected by NetVoucherCodes, there was a fee for a carry-on bag ($27), a checked bag ($41), and seat selection, but that was only $1.

According to the research, for the selected flight, "fast track" service—presumably Allegiant's Priority Access, which allows passengers to board the plane ahead of general boarding—was another $11.50. (Per Allegiant's website, this fee typically ranges between $4 and $12.)

In total, NetVoucherCodes found that Allegiant had a total of $80.50 in hidden costs, whereas the flight itself was only $75. When adding in the extra fees, the flight total was 107 percent more expensive.

RELATED: Alaska Is Cutting Flights to 14 Major Cities After This Year.

United Airlines also charges some hidden fees, making flying "the friendly skies" slightly more expensive, according to NetVoucherCodes' study.

While United doesn't charge for a carry-on, for a $55 flight, there were $67 in hidden fees, including $35 for a checked bag, $10 for seat selection, $14 for insurance, and $8 for onboard WiFi. With these tacked on, the flight was 122 percent more expensive.

JetBlue claimed the number five spot, charging for a carry-on ($30), a checked bag ($30), as well as seat selection ($6). The airline also has a fast track program that gets you through security faster, which came out to $15 for NetVoucherCodes' flight analysis, but onboard WiFi was conveniently free.

In total, for a $55 flight, there were $81 in hidden fees. When adding those on, the flight was 147 percent more expensive.

RELATED: Major Airlines Now Want to Weigh You Before Flights.

This one may be more surprising, but Delta Airlines clocked in at number four.

For a $55 flight, a carry-on was included, as was onboard WiFi. However, seat selection was the highest of all 10 carriers on this list, coming in at $30, per NetVoucherCodes' data.

Insurance was also pricey, at $27, but a checked bag was average, at $30. In total, hidden costs amounted to $87, and when adding them to the base fare, the flight was 158 percent more expensive.

Ultra-low-cost carrier Sun Country Airlines is also known for some sneaky fees.

For a flight with a base fare of $49, total hidden costs were almost twice that, coming in at $98.48. When adding these to the base fare, the flight was 201 percent more expensive.

According to NetVoucherCodes, Sun Country didn't offer WiFi, but a carry-on bag was $28, a checked bag was $32, fast track service was $12, seat selection was $9, and insurance was $17.48.

RELATED: Frontier Closing Check-In an Hour Before Flights—Will More Airlines Follow?

The second worst offender regarding hidden fees is Frontier Airlines, another budget carrier. However, "budget" is a bit of a misnomer, as your flight can quickly become much more expensive.ae0fcc31ae342fd3a1346ebb1f342fcb

While the base fare selected by NetVoucherCodes was just $29, hidden fees came out to a whopping $109, jacking the total cost up by 376 percent.

Per the website's data, a carry-on was $29, while a checked bag was the most expensive of the bunch, at $65. Seat selection was average, around $15, but there were no options for insurance or onboard WiFi.

This might not be a shock, but Spirit Airlines claimed the top spot.

According to NetVoucherCodes, the flight was one of the lowest, at just $21.89, but the hidden costs quickly added up to $161.13.

"Our study shows that while Spirit Airlines' flights seem cheap, passengers are paying up to 736 percent more in hidden charges, a bigger increase than any other airline in the world," a press release provided to Best Life reads.

Fees included $57 for a carry-on, $54 for a checked bag, $9.99 for fast track, $3 to choose your seat, $29.15 for insurance, and $7.99 for WiFi access.

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