Battery-electric seems an obvious no.

Would fuel cell electric count? I assume synthetic fuel (net-zero carbon, electrolytic hydrogen process, etc.) would not count.

I think the synthetic fuel option is actually reasonably likely.

@EvanDaniel to be honest I won't pretend to be competent for this judgment call, even if ideally it should have been stated beforehand. What do you and @ElliotDavies think?

@HenriThunberg Personally I think that these are three very different questions:

• Battery electric flight

• Fuel cell or otherwise electric drive train but running on fuel

• Synthetic fuel but conventional jet engines

I think you should include the first, second is a judgment call, third should not be included. I think either answer is fine on the second case, just pick one and make it clear. There's enough traders on this question to suggest that making a second version of it so that both versions exist might be interesting.

Cursed gettyimages cover picture generation

Do lighter than air aircraft count?

@TonyBaloney emm if it'scommercially viable so that I can book it as an individual, then sure.

Great question! How would you resolve a H2 or NH3 fuel cell with electric propulsion?

By "Start and landing" do you mean it could be fossil fuel all the way up to cruise level and then electric?

@NiklasWiklander I unsuccessfully spent 60 seconds trying to find something like a fuel-density over in-flight time graph. Suggestions? Basically I imagine ≥80-90% should be electric, but I am unsure to what extent that answers your question.

Maybe "commercially marketed as fully electric", and accepted as such by public audience including critics, is a better resolution criteria? Or at least an aid in the direction to think about it.

@HenriThunberg I found this: https://aviation.stackexchange.com/questions/47262/how-much-fuel-is-used-for-the-different-phases-of-the-flight-of-a-typical-airlin

A somewhat qualified guess on my part (lots of sim-flying, aerospace college) is that for London-NY about 10-15% of the fuel is spent getting up to cruise level. So your 80-90% would allow for a climb to cruise using jet engines.

@NiklasWiklander thanks! I am happy with allowing this then. Are you? Significant fuel cuts and certainly an 80/20 improvement to the current state.

@HenriThunberg As long as it's clear to everyone what the resolution criteria are, I'm happy. :)

I've been thinking about this as a good part-way-solution for a while. There is such a ridiculous difference in power required for takeoff/climb compared to just cruising along. Low hanging fruit.

Most likely lots of R&D going into this already, however I'm still doubting that this will happen before 2040, hence my big bet on no.