but what about the cost of all this? at the moment, liquid hydrogen is significantly more expensive than conventionaljet fuel, but backers of hydrogen planes believe it will eventually become cheaper than traditional flight. zeroavia isn't the only company racing to reimagine air travel, though. aerospace giants like airbus and boeing are also developing hydrogen planes. but there are still questions over how sustainable they'll actually be. we're going to be using some fairly exotic materials that are very energy intensive to arrive at. what energy are you using to build the fuel cell? what materials are you using? how much energy are we sinking into this technology to get something out? zeroavia has the backing of the uk government and big investors and has over 2,000 pre—orders from airlines. so there seems to be significant belief in hydrogen despite all of the challenges.