United Airlines today said it had ordered 40 new 737-700 aircraft from Boeing.
United said the order of the 150-seat aircraft, worth in total about USD 3.2 billion by book price, will enter service in mid-2017.
They will replace the some of the capacity currently served by smaller, 50-seat aircraft operated by United's regional partners.
"Our customers have a preference for an improved travel experience, including first-class seats, Economy Plus, and wi-fi. These aircraft are an efficient way to met those needs while reducing 50-seat flying," said United's acting chief financial officer Gerry Alderman in a statement.
United parent United Continental Holdings reported a 2.7 percent decrease in operating revenues for 2015 to USD 37.9 billion, due to lower passenger unit revenues.
But operating net income more than doubled to USD 5.2 billion helped by a plunge in fuel costs.
Net annual income increased more than sixfold, to USD 7.3 billion.
But full-year adjusted earnings of USD 11.88 per share missed market estimates of USD 12.00.
Shares in United dropped 1.1 per cent to USD 44.63 in pre-market trade.
