Specifically, the law — named the FAA Extension, Safety, and Security Act of 2016 — states that domestic and foreign air carriers "promptly provide to a passenger an automated refund for any ancillary fees paid by the passenger for checked baggage if":
The carrier fails to deliver the checked baggage to the passenger within 12 hours of the arrival of a domestic flight or within 15 hours of the arrival of an international flight, and
The passenger has notified the carrier of the lost or delayed checked baggage.
The law gives the U.S. Department of Transportation up to one year to issue final regulations regarding this fee refund, however. So details such as the specific number of hours could change slightly.
