Yeah I’d imagine most of the reasons sited from this hat wiki article don’t apply to an electric plane. But yeah air density would definitely be an issue but I thought the nasa Helios flight showed 90k to be the upper limit? So figured pushing to bear that altitude could be achieved and possibly beneficial since it would avoid bad weather and reduce drag... I guess was imagining the bulk of the engine power would be consumed at the start of the flight to reach altitude and then from there mostly glide until descending to land... but I’m not an aviation engineer at all just dreaming of quieter sky’s and less pollution