British Airways’ parent company International Airlines Group (IAG) has reached a deal to buy up to 42 777-9 aeroplanes from Boeing for a consideration of up to $18.6bn.

The commitment includes 18 orders and 24 options for the new 777-9, which is set to be available next month as the world’s largest and most efficient twin-engine passenger jet.

The agreement is part of British Airways’ efforts to modernise its fleet to more efficiently serve its global route network.

The airline previously procured the 787 Dreamliner family to replace its medium-sized widebody jets.

“The 777-9, in particular, simply has no competitor in its class when it comes to efficiency and performance.”

With the latest commitment to purchase the 777-9s, British Airways intends to replace its larger widebody aeroplanes, mainly the four-engine 747 jumbo jet.

The 18 orders will replace the airline’s 14 Boeing 747-400 and four Boeing 777-200 aircraft between 2022 and 2025. Each 777-9 aircraft will be powered by General Electric GE9X engines and will have 325 seats in four cabins.

IAG chief executive Willie Walsh said: “The new B777-9 is the world’s most fuel-efficient long-haul aircraft and will bring many benefits to British Airways’ fleet. It’s the ideal replacement for the Boeing 747, and its size and range will be an excellent fit for the airline’s existing network.

“This aircraft will provide further cost efficiencies and environmental benefits with fuel cost per seat improvements of 30% compared to the Boeing 747. It also provides an enhanced passenger experience.”

British Airways’ fleet includes nearly 60 777 long-range jets. Last year, the airline agreed to procure four additional 777-300ER (Extended Range) jets via operating lease.

With a slightly wider cabin than the current 777s, the new 777-9 aircraft can accommodate between 400 and 425 passengers in a standard two-class cabin.

New enhancements made by Boeing will ensure 12% lower fuel consumption than competing airplanes. The 777-9 comes with a standard range of 7,600nm.

Boeing Commercial Airplanes president and CEO Kevin McAllister said: “The 777-9, in particular, simply has no competitor in its class when it comes to efficiency and performance. It is the right-sized airplane for British Airways to efficiently serve long-range routes with heavy passenger demand.”

The company started production of the 777X in 2017 and the first delivery is expected to take place in 2020.