• Electric batteries in their current form would make a long-haul flight too heavy to take off. Only a massive step-change in battery density, nearly tripling the energy density every decade for the next three decades, could solve this challenge.

• A large aeroplane using liquid hydrogen combustion would be able to take off and land, but a large
cryogenic tank and supporting infrastructure is lacking. An LH2 combustion aircraft would also produce significant contrails that would need to be further studied. Using fuel cells would further increase the cost and take-off weight.

• Flying using liquid methane would enable a widebody to take off and land. It poses a number of technical challenges and high cost, even if the necessary infrastructure is closer to being ready.

• Ammonia produced from green hydrogen is deemed a promising hydrogen carrier. Nonetheless, its use would lead to an excessively heavy long-haul aircraft.

• To have enough solar panels to power an A380, you would need to cover the plane – and add at least 7.4km of panels behind, making this the least practical solution of all.

• All of these solutions would require colossal amounts of electricity to generate the required power. To decarbonise all EU27+UK long-haul trafficby 2050, aviation would need between a net square of 24 km to 35 km of solar photovoltaic panels at the average EU solar irradiance 3.98kW/m2/day, or 2,853 to 6,374 offshore 20-MW wind turbines or 10% to 23% of all EU electricity.

• The level of decarbonisation depends largely on the carbon intensity of electricity used during the entire process from well to wake. Wind-generated electricity shows a remarkable CO2-eq reduction of -79% to -96% compared to conventional jet fuel. Photovoltaic electricity may have a slight decrease in CO2-eq reduction efficiency, ranging from +7% to -69%. Utilising coal-sourced electricity for flying using these solutions could increase the CO2-eq emissions by 3 times (for battery aircraft) to 11 times (for liquid hydrogen fuel cell aircraft).