This field of tech should have a good niche in air travel.

Batteries will likely never be viable, aside from the lower energy density you have to carry them after they are exhausted. That a jumbo jet get significantly lighter as it travels is a boon.

30,000 feet is a particularly bad place for exhaust, but the issue with burning gas isn't so much the pollution, but that you are digging up carbon that has been sequestered for millions of years faster than stuff like coffee beans can gobble it up again.

It pays to be conservative when you are... flying in the face of gravity. Even if something like a fuel cell proves viable it won't have the century of refinements & safety standards.

Resources spent on electric flight would be better invested here or on cargo ships.