Southwest Airlines will start charging passengers to check bags for the first time. It’s a stunning reversal that shows the low-cost pioneer is willing to part with a customer perk executives have said set it apart from rivals in more than half a century of flying in hopes of increasing revenue.

Southwest Airlines will end its decades-old policy allowing "bags to fly free" as their marketing put it. Starting in May, passengers will be required to pay for checked bags. Travelers who claim to be loyal customers of Southwest are sounding off after the airline announced changes Tuesday to its popular passenger perk.

The changes include bag charges, more restrictions and fewer points for basic economy, expiration dates on credits, and dynamic pricing for point purchases.