Last year, aircraft manufacturer Airbus patented a hybrid electric jet engine for airliners which can be powered by both conventional kerosene and electricity.

The XCOR team then developed a more powerful engine with an advanced pump-fed fuel system for a larger aircraft now being flight-tested for a commercial customer.

When GE was selected by the Chinese as the engine provider for the aircraft in 2002, the companies estimated that about 500 ARJ21s would be sold over 20 years, with a potential value of $3bn to GE.