Frontier Airlines will begin charging some customers for carry-on baggage this summer, the next step in Frontier's transformation into an "ultra low-cost" airline.
The Denver-based carrier says the fees will be charged only to customers who purchase its least expensive "basic" fares through "outside booking channels" such as online travel websites.
Frontier's "most loyal customers" - those who have reached the levels of "summit" and "ascent" in Frontier's EarlyReturns frequent flyer programme - will not be subject to the fees, says the airline.
The carry-on fee will range from $25 to $100 and the effective date will be "announced later this spring", the airline says.
Customers who purchase more-expensive "classic plus," "classic" and "economy" fares will also not have to pay the fee, regardless of where they book.
Frontier said it is implementing the carry-on charge in response to frustration by customers at being unable to find available space in overhead bins.
Frontier now joins the ranks of Spirit Airlines and Allegiant Air, which also charge for carry-on luggage.
Starting in June, Frontier will also increase to $25 the at-airport charge to check a first bag, up from $20.