/r/solarpunk is a sub for those interested in “solarpunk aesthetics” which means carbon free degrowth utopias for their scifi stories/games, etc.
Naturally their zero CO2 emissions world has no place for planes.
https://old.reddit.com/r/solarpunk/comments/113j3et/how_do_we_travel_overseas_in_a_solarpunk/
A bit arduous is quite an understatement
Once we get rid of capitalism everyone will be free to sail around the world 
This is literally how it was done for all of history until the mid-1800s.
Sailing across the oceans was quite dangerous back then, I doubt redditcels will enjoy being in the middle of the Atlantic during a storm.
https://old.reddit.com/r/solarpunk/comments/r267s1/the_future_of_long_distance_air_travel_airships/
sail boats. people will have a lot more time to travel. in fact the voyage will be as important as the time spent in the destination, if not more important.
in fact i'm willing to bet that, in the future people will spend way more time travelling the world than we do now. because our "union" will not be because we share products it will be because we will share experiences.
humanity will not be tied economically it will be tied because we, our friends and family will have shared real experiences all around the world. no longer people will look at someone else from another country as another species because we will all travel around the world.
Bonus, some discussion on their meme ideologies
https://old.reddit.com/r/solarpunk/comments/1bbgodf/political_ideologies/
Oh no !neolibs bros 
Lot's of “wholesome degrowth”
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The only thing I can think of would be truly frickoff massive glider/airship combos which would have to be sufficiently massive to carry their own batteries. Eventually, you could get an airship to do it, but it would be monstrously expensive and inefficient. You would just have to keep massively increasing the size until it held enough batteries to overcome its own drag on the flight there. That would actually be a sort of cool idea that isn't fricking gay like that sub is. Almost a sort of rightoid solar punk where only the wealthy elite could fly.
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!math hydrogen lifts about 1.2kg per cubic meter, good lithium batteries are about 250Wh/kg. 11,000km range, 100 seats, energy = efficiency * distance * seats.
I got about 880,000kg of batteries and 733,000 cubic meters of hydrogen. I assumed about 200Wh/km for the efficiency based on googling “how efficient are electric aircraft”.
I did not include air resistance because rigid airships are so slow that it's not very relevant.
I assumed 125 bucks per kWh for batteries. So this machine costs 27.5 million dollars in batteries alone. A 777 probably does cost more than that, I think they run like 300 mil, so this idea is only stupid for the other sixteen thousand reasons it's stupid.
That all check out?
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Almost a ton of batteries and hydrogen gas sounds like an absolutely safe combo, nothing to see here
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I literally don't care if the passengers die, that's for the engineers to worry about. Also it's 880,000kg of batteries, it's 880 tons.
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Why should I care if the passengers die? Let the bean counters solve that shit.
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https://en.wikipedia.org/wiki/Nuclear-powered_aircraft there were several engine prototype constructed. I think one of the designs was just putting a small nuclear reactor in the combustion chamber of a turbojet engine, so it would go white hot and heat the air directly, no gay intermediate working fluids or anything like that. Naturally under such conditions it would ablate and produce highly radioactive debris in the exhaust.
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That's bad as shit. Frick a working fluid, air is going to do whatever the frick we want it to.
Can we throw a massive magnetron in there as a preheater or something just so we also have high voltage and emissions in the microwave range? Please dad I really want this thing to kill people.
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