United Airlines has ordered 40 Boeing 737-700s as part of its programme to retire small regional jets.
Deliveries of the 737s will begin in the middle of 2017 and will allow the Chicago-based carrier to reduce its fleet of 50-seat aircraft by more than half by 2019, it says.
United had 256 50-seat regional jets at the end of 2015.
"These aircraft are an efficient way to meet those needs while reducing 50-seat flying," says Gerry Laderman, acting chief financial officer of United, citing improved passenger comfort and additional amenities on the 737s compared to the smaller jets.
The airline had considered the 110-set Bombardier CS100 and both the 90-seat Embraer 190 and 120-seat E190-E2 aircraft for a small mainline narrowbody order.
United configures its 737-700s with 118 seats.