LONDON, Nov 28 (Reuters) - Britain's Rolls-Royce (RR.L) said it has successfully run an aircraft engine on hydrogen, a world aviation first that marks a major step towards proving the gas could be key to decarbonising air travel.The ground test, using a converted Rolls-Royce AE 2100-A regional aircraft engine, used green hydrogen created by wind and tidal power, the British company said on Monday.It said in February it planned to fit a specially adapted version of a current generation engine near the back of an A380 superjumbo test plane.Other technologies backed by companies such as Rolls-Royce include electric engines, which would be initially suitable for short flights, and sustainable aviation fuel (SAF).It could eventually be produced by combining carbon captured from the air with green hydrogen, but the process is energy intensive and not yet available on a large scale."