Southwest Airlines has put a price tag on checking bags, a coveted free perk that is about to disappear as part of substantial changes the carrier is making to its service.

It’s the last day to book a flight on Southwest Airlines without being hit with a fee to check bags after the airline abandoned a decades-long luggage policy that executives once described as key to differentiating the budget carrier from its rivals.

Southwest Airlines is ending some of its long-standing policies in order to capture ancillary revenue. How much will they make from charging for bags?