is due to enter service in 2013 on the Mitsubishi MRJ regional jet and the CSeries. CFM International is developing the Leap X turbofan/open rotor for service readiness from 2016, while Rolls-Royce is exploring developments.

Airbus is expected to decide whether to launch a re-engining upgrade for the A320 before the end of 2010 for a service entry in around 2015, with the GTF seen as a leading candidate. Boeing chief executive Jim McNerney has said he believes a re-engined narrowbody is viable in the near term and that a derivative re-engined 737 would cost in the range of 20-30% of a full development programme.

As a result, he says, "the re-engine case is stronger than I anticipated it would be, which doesn't mean that's what we'll decide". CFM hasindicated it could accelerate the Leap X schedule - set for certification in 2016 - should it be selected to power China's new C919 airliner, which would open the door for Boeing to consider the engine for any 737 upgrade.

One of the drivers behind the two rivals' reluctance to be the first to blink is that their sales performance in the sector is fairly evenly matched. Last year, Airbus racked up 472 A320 family orders, and delivered 386 aircraft, while Boeing's 737 sales stood at 484 and deliveries at 290 (strike affected). In 2009 the 737 has a slight edge on its rival at the nine-month point with 71 net orders against 47 for the A320.

Deliveries are evenly matched, with Airbus having shipped 290 single-aisles and Boeing 280.