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.

Customers will be charged for their first and second checked bags unless they hold top-tier loyalty status or are traveling on a business fare.