Bags no longer fly free on Southwest Airlines for any fares purchased from May 28 forward. However, Southwest cardholders will receive one checked bag for free.

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."

Times have changed, and one of the pillars of its business model -- "bags fly free" -- has finally fallen by the wayside. Here's what travelers need to know.