[sjwright]

Hybrid electric jet engines are being developed, and have real potential to improve fuel economy. A substantial improvement in fuel economy could mean carrying less fuel, which in turn improves fuel economy.

But if you’re talking about plug-in electric, the challenge is presumably battery weight versus fuel weight.

[sp332]

Yes, they'll still probably have to carry liquid fuel because nothing else has the energy density required. But maybe we can make this fuel from a carbon-neutral source instead of oil pumped out of the ground.