Just a pointer to a cool project which appeared on Hackaday: a solar powered FPV plane that can fly forever (or at least until the sun goes down). Pretty spiffy!

The comments show a link to this solar powered plane developed at ETH:

It was in the air for 81.5 hours, and had a continuous flight distance of 2316km. It’s a slow flyer: average speed is just under 18mph. At the end, you can see that the wind conditions had deteriorated seriously. Pretty nifty.