Southwest Airlines has updated its checked bag policy, and passengers will start paying extra tomorrow. Southwest has long allowed passengers to bring a guaranteed free checked bag, but that is changing tomorrow as the airline adopts a new policy.

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.

Earlier this year, the airline announced plans to end its trademark “bags fly free” policy to help shore up earnings.