Deliveries of the 737s, which join the 40 that the Chicago-based carrier ordered in January, will begin at the end of 2017. United will use them as part of its programme to reduce its 50-seat regional jet fleet to fewer than 100 aircraft by 2019.

United will also add nearly 100 Embraer 175s with 76 seats to its feeder fleet as part of the 50-seat jet reductions.