United Airlines has become the second US carrier to restart services operated aboard the Boeing 737 Max with a flight between its Denver and Houston hubs.

American Airlines began flying the aircraft in late December with flights out of its Miami hub, and prior to that Brazilian low-cost carrier GOL was the first carrier worldwide to resume 737 Max flights.

Southwest Airlines and Alaska Airlines plan to begin flying their Max fleet next month. Canadian carriers WestJet and Air Canada have also returned the jetliner to service, and European aviation authorities have also cleared the aircraft to fly once again.

The aircraft was grounded in 2019 for 20 months following two deadly crashes, but in November 2020 was cleared to fly once again by the FAA following extensive software enhancements, design changes and a revamped pilot training program.

United has promised to tell passengers what kind of aircraft they will be flying at the time the reservation is made. The carrier is offering passengers the option of changing to a different flight not operated by the 737 Max if they choose to.

If a passenger who is booked on a 737 Max wants to change, United said, the airline will rebook the traveler on a substitute flight at no charge or refund the ticket. All United routes will have non-737 Max options, with at least half the flights on each route using other types of aircraft.

united.com