If you’ve ever bought a plane ticket and wound up paying far more than the touted fare, the Department of Transportation is here to help.

Starting January 24, airlines will be required to include all government taxes and fees in their advertised prices.

For more than two decades, airlines and travel agencies have been allowed to list government-imposed fees separate from the actual fare, resulting in reams of fine print and disclaimers about charges that can add 20 percent or more to a ticket’s price.

But then internet fares came along, bringing with them a menu of fees for services that used to be part of the ticket price — and consumer complaints soared. In 2011, theDepartment of Transportation  assessed 21 penalties for fare advertising violations, with total fines of more than $1 million.

So now the Obama administration has stepped in and issued a mandate for transparency, with transportation department spokesman Bill Mosley saying, “Requiring all mandatory charges to be included in a single advertised price will help consumers compare airfares and make it easier for them to determine the full cost of their trip.”

Optional fees, such as those assessed for baggage or booking online, are not included in the new rule since those charges are avoidable and not required to purchase the ticket.

While travelers and consumer rights groups applauded the new requirements, many airlines are less pleased. In fact, low-cost carriers like Southwest, Spirit, and Allegiant are going to court, arguing that the mandates violate corporate free speech rights.

But Eugene Volokh, a law professor at the University of California, Los Angeles, said they may not have much of a case, adding, “The Supreme Court has said in the context of commercial advertising, the government has a very broad right to mandate speech that is reasonably aimed at preventing people from being misled … I think, therefore, most likely [the new rules] will be upheld”

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