Unbundling comes with its own share of obstacles.

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As airlines have unbundled airfares, adding fees for baggage and seats and other amenities, customers have become confused as to what is included in the price of a ticket, according to airfare analysis company Hopper.

“Although unbundling arguably allows travelers to avoid paying for services they don't use, it's also a major cause of dissatisfaction since consumers are often confused about what's included and what isn't,” Hopper's chief data scientist Patrick Surry wrote in his analysis.

The move toward unbundling means that airlines can advertise a low price that increasingly does not include baggage fees, seating selection, and cancelation or change fees.

Hopper calculated a “total cost” for flights on different airlines based on median airfares, change fees, and baggage. While the median airfare—which customers might consider the price of a ticket—was $496 on American Airlines, the “total cost” was $780. On JetBlue, median airfare was $448 but the total was $683. Read the anaylsis.

The study found that international travel tended to be more lenient than domestic flights, when it came to cancelation fees and free luggage, with approximately two-thirds of international flights offering at least one free bag.

Despite this reported confusion among passengers, airline travelers have cited à la carte pricing as one of their most sought after characteristics when choosing a flight. Two-thirds of passengers surveyed in a 2016 Ipsos Public Affairs survey commissioned by Airlines for America said they preferred this pricing model.

Hopper released a new feature to combat some of these hidden fees called “Fair Bear” that allows app users to filter out flights with ancillary fees when browsing through price options.

The U.S. Department of Transportation (DOT) has similarly put pressure on airlines to show more transparency when advertising their flight prices, proposing a new rule in January that would require airlines and outside ticket agencies to advertise their ticket prices while including checked luggage and carry-on prices.

“This proposal from the DOT is a step in the right direction to require air carriers and ticketing agencies to provide customers with critical information up-front on potential fees,” Senator Chuck Schumer said in a statement shared with Travel + Leisure. “Hammering travelers with hidden fees is downright wrong.”