United Airlines has made a firm order for 25 of Airbus’ A350 extra-wide bodied jets worth an estimated US$6 billion, fulfilling a commitment signed in December, the European aircraft manufacturer said recently.

Deliveries of the A350-900s are scheduled to begin in 2016 and run through 2019, Airbus said in a statement.

The order is half of a 50-aircraft order United announced in December, when it also unveiled plans to buy 25 of Airbus’ rival Boeing Co.’s 787 Dreamliners.