A U.S. Senate subcommittee has held a hearing to question the growing use of airline fees to charge passengers for things like early boarding and better seats.

An American Airlines Boeing 737 Max 8, on a flight from Miami to New York City, comes in for landing at LaGuardia Airport on March 11, 2019, in the Queens borough of New York City. Boeing's stock dropped more than 12 percent at the open on(CNN) - United Airlines passengers fearful of boarding a Boeing 737 Max will be able to rebook flights for free once United starts flying the planes again. Nocella said it's probably too soon to tell what passenger reaction will be once the 737 Max returns to service. A spokesperson said that if a passenger does not want to fly the 737 Max, "we will offer them full flexibility." It's unclear when the 737 Max will return to the skies.