Here is a cool plane that is good for 10 hours in the air using fuel cell. Of course Musk says fuel cells are dumb.

HYWINGS hydrogen fuel cell UAV demonstrator, powered by HES (1 min 32 sec)

I started out in rc airplanes in 2011 or so and after becoming familiar with rc and servos I eventually got involved in building Arduino controlled robots. Here is my last project: a scratch built seven servo Arduino robot using standard size servos. Kind of fun project but spent too much time programming it.

Bipedal StriderBot: Robot Moves (4 min 25 sec)