Frankly there isn’t a replacement fuel even close to the composition that will be necessary for use as a ‘drop-in replacement’ for all aircraft/helicopters in all operating conditions globally… People need to stop fixating on the narrow range of operations/types (fixed and rotary) that seem to be mentioned over and over and over with some key important combinations of engine type/operating environment/use, being overlooked. I predict that we are looking at least until 2030 before a suitable fuel is formulated and PROPERLY AND FULLY TESTED IN ALL CIRCUMSTANCES and in ALL possibly engine/airframe combinations in a robust way, as this is more critical than most people realise…