The new Airbus planes, which will be delivered in 2024, will allow United to retire its Boeing 757-200s, the company said.
The Airbus order is the latest blow to the American manufacturer, already deeply mired in the crisis surrounding its 737 MAX.
Boeing, whose 737 MAX has been grounded worldwide after two crashes that resulted in 346 deaths, currently has no new aircraft to compete with the Airbus A321XLR in the mid-market range.
Airbus launched the A321XLR only this year, at the Paris Air Show in June.
The single-aisle aircraft’s range is 15 percent above that of its predecessor model, the A321LR, making it a cost-effective alternative to long-haul wide-body planes.
United said it intends to use the new aircraft to serve additional European destinations from US East Coast hubs in Newark/New York and Washington.
United turned to Airbus for the purchase due to Boeing’s lack of aircraft in the mid-market range, a source close to the matter told AFP on condition of anonymity.
“There are no aircraft currently offered by Boeing that can replace the 757,” the source said, adding that negotiations between Airbus and United began several months ago.
Boeing, which is currently focused on returning its MAX aircraft to the sky, has already postponed possible announcement of a new model aircraft until next year.
The manufacturer recently presented the design to various airlines, industrial sources said.
Airbus decided to no longer publish the catalog prices for its aircraft beginning in 2019. However, the A321XLR is a long-range version of the A321, whose unit value was $129.5 million in 2018.
United has meanwhile postponed receipt of its first 45 Airbus A350 long-haul aircraft by five years.
The company, which ordered the planes in 2017, said it now plans to have them delivered in 2027 instead of 2022.