With the climate crisis accelerating and the EU aiming to reach net-zero emissions by 2050, every industry that emits greenhouse gas emissions must be targeted ­— and the consensus is that aviation will be the toughest sector to decarbonise.

Air travel is responsible for 2% of worldwide carbon emissions — last year accounting for 915 million tonnes of CO2 — and, pre-coronavirus, passenger numbers were expected to shoot up some 70% by mid-century.