Just over 20 years ago, a small model aircraft (https://en.wikipedia.org/wiki/The_Spirit_of_Butts%27_Farm) crossed the Atlantic in 39 hours using about a gallon of Naptha as fuel. The same year, the Design-Build-Fly club at my university built an electric aircraft which had some serious endurance and payload capabilities, though I don't remember the details. Keeping a model electric plane aloft for a day is impressive, but how many hobbyists have built something similar by now without any expectation of VC money?