Orders have been confirmed for 18 Boeing 787 Dreamliners worth an estimated $4 billion for British Airways.

This is in addition to 24 of the aircraft and 12 Airbus A380s ordered by BA parent International Airlines Group as part of a fleet modernisation plan unveiled in 2007.

The long-haul twinjets would replace some of BA’s fleet of Boeing 747-400s between 2017 and 2021, IAG said.

IAG is also talking with Boeing on the commercial conditions for an order of 787s for Iberia, adding the carrier had first to complete its cost cutting restructuring.

The firming up of the 787 options for BA comes as Boeing comes close to concluding testing of a revamped battery system for the new generation aircraft.

Dreamliners have been grounded since January due to overheating of lithium-ion batteries on two of the aircraft. Boeing hopes the aircraft can resume operations in May or June.

The manufacturer has taken orders for 42 Dreamliners this year, bringing the order book up to 841.

IAG chief executive Willie Walsh said today : “British Airways has 24 Boeing 787s on order already and we plan to boost this by a further 18 aircraft by exercising our options.

“The aircraft offers a step change in fuel burn efficiency versus our existing aircraft with improvements in fuel cost per seat of more than 20 per cent. New technology engines and improved aerodynamics will lower fuel burn leading to reduced carbon and NOx emissions.

“The creation of IAG has resulted in greater buying power for both airlines through joint procurement and we have been able to obtain delivery slots for Iberia as part of British Airways’ order.”

BA has 118 wide-bodied long haul aircraft in its fleet with 42 aircraft – 12 A380s, 24 787s, six 777-300ERs – already ordered.