SO WHAT? Aviation company says it flew aircraft with hydrogen fuel cell. These are only interesting or useful in a world where hydrogen is cheap and plentiful. Right now we generally make it via steam reformation of natural gas, which means you’re still working from fossil fuels. You can also split it from water via electrolysis, which you could do if you had lots of nice clean nuclear plants, or plentiful orbital solar power, neither of which is available or scheduled. That doesn’t make this research worthless, but . . .