Future Timeline

What fuel is going to replace jet fuel? I hear they are working on hydrogen fuel or Bio fuels being more evermental friendly. But I hear Bio fuel are more expensive than jet fuel. Also with the rising cost of jet fuel now it may be cheaper to switch over to hydrogen fuel.

So what sustainable aviation fuel be cheaper than jet fuel? As the price of jet fuel is extremely costly now compared to 60 years ago. And if any thing in the next 20 years the price of jet fuel will be even more costly.

Bring on the nuclear powered jets!

Biofuels/hydrogen are the obvious choice for the near-term.

Medium to longer term, battery-electric and hybrids. These will initially be used on smaller aircraft and short-haul routes, but eventually scaling up to the largest commercial airliners, perhaps by 2045-50.

Further out, solar power might be another possibility, but mostly for smaller to medium aircraft, unless combined with batteries.

I can't see nuclear playing a role in aviation, except perhaps in niche/experimental aircraft.