New regulations from the Transportation Department require airlines to include all mandatory taxes and fees in advertised fares.
Until now, the department has allowed airlines and travel agencies to list government-imposed fees separately.
That can add 20 percent or more to a ticket's price. The advertising rule will go into effect January 26th.
Southwest Airlines, Allegiant Air and Spirit Airlines have filed appeals to have the rule overturned,
arguing that it violates commercial free speech rights.
Other passenger protections that also go into effect next month include a ban on prices increases after a ticket has been purchased.
And a 24 hour window to hold or cancel a reservation without penalty.