But with the advent ofimproved lithium-polymer batteries, similar to what you'd find in a laptopcomputer, hybrid aircraft – albeit at asmall scale – are now starting to become viable.

The team is also preparing a second hybrid wing body aircraft, the X-48C for future flight tests.

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