what's a somewhat believable future alternative to planes? i.e. some kind of method for sustainable inter-continental passenger/cargo transport

context: i'm writing a story set in a world that is clearly in the far future (it's populated entirely by sentient androids), but technology has stagnated somewhat, so things haven't really gotten that futuristic. the androids are the biggest advancement, but that's mainly because they evolved on their own after humans died out.

the tech doesn't necessarily need to be Realistic, it can still be a bit sci-fi if needed, just nothing that would make it seem too magical.