Spirit and Allegiant airlines charge between $25 and $50 for carry-on luggage.
Checked baggage fees have become a fairly common industry practice. But some airlines are starting to charge for carry-ons, too.
Spirit and Allegiant both charge between $25 and $50 for carry-on luggage,depending on whether a passenger pays the fee when they book online or check in at the airport.
The rationale behind this move: Carry-ons extend the time it takes to a board the plane, costing the airline precious minutes.
"The unintended consequence of charging for checked bags is that people bring them on board. People get into fistfights and the planes are delayed..." said George Hobica, founder of airfarewatchdog.com. "It all adds up minute wise, keeping the plane on the ground longer."
Allegiant spokeswoman Jessica Wheeler said other airlines charge higher fares to absorb these costs. By charging the fee only to people who bring bags on board, it allows the airline to continue to offer budget fares, she said.