Spirit Airlines fined for tweets, ads

The fines come under the "Passengers' Bill of Rights" that was implemented by the DOT in 2010.

“Consumers have a right to know the full price they will be paying when they buy an airline ticket,” Transportation Secretary Ray LaHood said in a statement. “We expect airlines to treat their passengers fairly, and we will take enforcement action when they violate our price advertising rules.”

DOT has penalized companies before for violating its new rules for passenger protections, including recently fining popular airplane ticket sales website Orbitz.