(CNN) -- That airfare you booked because it looked like a great deal can actually end up costing you 50 percent more because of extra airline fees, a watchdog group has found.
The Consumer Travel Alliance analyzed the base fares and extra charges for nine major airlines on four popular domestic routes.
It found that a traveler requesting extra legroom and checking two bags would have to pay an average of 54 percent more than the base price of the ticket shown on a popular online travel site at time of purchase.
For a family trying to book a trip, the fees can mean hundreds of dollars in unanticipated expenses, said Charles Leocha, director of the Consumer Travel Alliance.
"It shocked me that American consumers basically have to [shop] with a blindfold on," Leocha said.
"By having all these hidden fees, the airlines are removing the ability from consumers to compare prices."
Leocha expressed frustration that websites like Travelocity and Expedia show base airfares only, while airline websites don't reveal the fees until the very end of the buying process.
The Consumer Travel Alliance wants Congress and the Department of Transportation to require airlines to disclose all fees at the time that they file their airfares, so travelers can get the whole picture.
Airlines fully support price transparency and a level playing field for all customers, said Jim May, president and CEO of the Air Transport Association, which represents some of the country's biggest carriers.
"Today, carriers disclose fares and fees on their Web sites, which their customers and other persons can readily access. Customers and third parties can apply that information to their particular needs," May said in a statement.
"The Department of Transportation has raised the issue of the dissemination of fare and fees in its proposed passenger protection rulemaking. This will provide an opportunity for all interested parties to express their views about the issue."
Last month, the DOT proposed requiring airlines to provide special notice whenever baggage fees are increased, and to notify passengers buying tickets whether they must pay to check up to two bags.