Less than a fortnight after the final 747 rolled off the assembly line in the US, Rolls-Royce debuted its biggest ever jet engine – just about able to pass through a London Underground tunnel.

As Boeing ditches the Jumbo Jet for lack of interest, Rolls-Royce is hoping UltraFan, unveiled on Monday, will help it to solve the problem of green air travel.

While aviation accounts for about 2.5pc of carbon dioxide emissions, the industry is under pressure to move towards zero emissions by 2050.

Around the world, engineers are attempting to crack the seemingly impossible challenge of fueling long-haul flying without generating large emissions.

For smaller craft, top-end batteries can be used for the shortest, taxi-like routes and hydrogen at low pressure may be deployed for short-haul flights.

Read more: The Telegraph