United Airlines has ordered nine more Boeing 787-9s, bringing its backlog for the type to 13 aircraft.
The jets will be used to replace older widebodies in United's fleet when they begin arriving in 2020, says the US carrier.
The order has a list-price value of more than $2.5 billion.
With the latest commitment, Chicago-based United has firm orders for 13 787-9s and 14 787-10s, based on its statements and Flight Fleets Analyzer. The carrier also holds 10 options on the 787-8.
United configures its 787-9s with 252 seats, which slots the aircraft between its 240-seat 767-400ERs and 276-seat 777-200s after the latter's ongoing Polaris and Premium Plus cabin reconfiguration.
The order comes as United plans to introduce its first 787-10, the largest Dreamliner variant, on flights between Newark and Los Angeles on 7 January 2019, and between Newark and San Francisco in February 2019.
United operates 12 787-8s and 25 787-9s, Flight Fleets Analyzer shows.