Travellers may be able to enjoy guilt-free "green" holidays within years thanks to eco-friendly aeroplane technology being developed in Britain.
Reaction Engines in Oxford has begun work on systems which will turn existing commercial aircraft "emission-free", by allowing them to run on ammonia rather than kerosene.
Ammonia would be safer than traditional kerosene because it is harder to burn and so less of a fire hazard, researchers say. When it does burn, it does so without CO2 emissions.
The system works by splitting ammonia into hydrogen and nitrogen, with the former burned to fuel the jet.
James Barth, the engineer behind the project, said there were key benefits to using ammonia over pure hydrogen. He said it meant commercial airlines would only have to adapt their existing fleet, rather than redesign models, and it would not mean higher air fares.
There has been a wave of trials of battery-powered planes, with companies such as Rolls-Royce, Airbus and Siemens looking into such projects.
But experts say the range of electric planes would be severely limited.
Ammonia-fuelled planes would be able to handle most short-haul flights, although the range is still less than that of existing planes.