Airlines may be on the verge of losing their fight against the Biden administration’s new promise of automatic refunds for canceled or delayed flights. On Tuesday, lawmakers relented to pressure following our reporting on the matter and purportedly included a provision guaranteeing the refunds in a must-pass Federal Aviation Administration (FAA) funding bill, which faces a looming Friday deadline.

How much might this new automatic refund guarantee cost the airlines?

Potentially billions, but consumers can’t be sure. For more than a decade, airlines have refused to say just how much in unused tickets they’re sitting on, or how much they make when many of those credits expire.