United Airlines has converted 10 firm orders for the Boeing 787 to the 777-300ER.
The 777s will be delivered from 2016, says the Chicago-based carrier. It cites the larger widebody's "attractive upgauge and range opportunities" as factors in the decision.
"These changes are part of our strategy to improve operational reliability, grow capacity with demand, and enable us to achieve our long-term goal to improve margins and return on invested capital," says John Rainey, United's finance chief, in a statement on the order and other fleet changes.
Flightglobal's Ascend Fleets database shows that United has firm orders for 48 787s, comprising 27 -10s and 21 -9s. However, the airline has not disclosed which variants it has converted to the 777.
The 777-300ER order is valued at $3.3 billion at list prices.
United had said in January that it was considering converting existing widebody orders to the 777-300ER.