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.

Starting on Wednesday, the Dallas-based carrier will charge customers $35 for their first checked bag and $45 for their second checked bag. The bag fee change will also apply to existing flight itineraries changed on or after May 28, Southwest confirmed to "Good Morning America."