Chicago-based United Airlines has ordered 25 Airbus A350 XWB aircraft and 25 Boeing 787 Dreamliner aircraft in an effort to maximise network flexibility, reduce costs and improve customer satisfaction.

The delivery of the new aircraft will take place from 2016 to 2019, when the airline will replace its fleet of international Boeing 747s and 767s.

With the acquisition of the 50 new aircraft, the airline will reduce the average seat count by about 19% and by about 10% when averaged over the entire international fleet.

The airline estimates it can reduce its fuel costs and carbon emissions from the 50 new aircraft by nearly 33% with the purchase.

The Airbus A350 aircraft will be powered by the Rolls Royce Trent XWB engine while the Boeing 787 will be powered either by the Rolls-Royce Trent 1000 or the GE Genx.

United also expects the average lifetime maintenance costs for the new aircraft to be reduced by 40% per available seat-mile, compared to its replaced aircraft.

The new aircraft will improve customer satisfaction by featuring larger windows, more overhead bin space and improved lighting.

United Airlines CFO Kathryn Mikells said the order provides teh company with the most efficient aircraft for its international network, providing the right range, size and operating costs for United’s diverse set of worldwide destinations.