The worlds biggest aircraft maker airbus unveiled historic designs for hydrogen-fuelled passenger planes on monday. a few days later, the worlds first sizeable aircraft to be powered by hydrogen took flight. it was piloted by start-up zeroavia, based in california and cranfield, england. a commercial launch might be just three years away, it says.

As aviation comes under pressure to curb emissions, investment in hydrogen is being stepped up. hopes of using battery technology as a green alternative to jet fuel are fading. batteries are just too heavy for long flights, given their low energy density. airbus, with rolls-royce, closed a demonstrator project in april.

Hydrogen has limitations too, but they are less serious. fuel tanks would need to be four times larger than those used now. the extra weight and space involved would probably make hydrogen uneconomic for long-range aircraft. costs per passenger could rise by as much as half, though by much less for shorter-range planes, according to mckinsey. more work needs to be done on efficient refuelling technologies. assuaging safety concerns will be vital. the hindenburg airship disaster was more than 80 years ago but retains a grip on the popular imagination.

Another objection is that it is costly and energy-intensive to make hydrogen. the limited green power available would be better used to electrify road vehicles, heating and industry. but hydrogen production can help scale up renewables because it can make use of intermittent energy sources. the eu is pushing green hydrogen hard, arguing that it could meet nearly a quarter of world energy demand by 2050. the uk government, which backed the zeroavia venture, is also keen.

Hydrogen has the potential to halve aircraft emissions, airbus says. mckinsey reckons it could be used in 40 per cent of all aircraft by 2050. that will not sway cynics who say hydrogens potential to be the fuel of the future is never-ending. but it is probably time to park that jibe.

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