Hydrogen is great per mass but horrible per volume. That's why it has to be cooled down past liquid into slush. Even then the tanks needed are enormous compared to jet fuel used now. Would require a complete redesign of airplanes - maybe larger lifting body aircraft or flying wings.

That would require a more space at airports. Maybe the supply chain is there but rebuilding all the worlds airports? That's a mess.

I do like biofuels because of the mass and volume energy storage and they drop into the supply chain really well.

The best way to stay carbon neutral is always to not build new stuff to replace working stuff. True for cars and I would bet even more so for airplanes.

Interesting discussion though, thank you!

This will be an unpopular opinion but that's okay.

I wish they would stop spending time on hydrogen. The energy density is so low unless you turn it into "slush" which takes an incredible amount of energy to do and becomes a really dangerous fuel. I worked on these projects at a fairly large industrial company.

It just doesn't work but governments pay for it to appease environmentalists and businesses happily take the money. They all know it's not the future.