This is a rather interesting video of Youtuber Brick Experiment Channel testing, building and flying a functional quadrocopter constructed almost entirely out of LEGO pieces (including motors and propellers -- I didn't know those motors had it in them). The only non-LEGO parts is the copter's battery, flight controller, and radio receiver. That's impressive. Maybe not as impressive as building and flying a functional quadrocopter made out of Lincoln Logs, but I suppose you have to start somewhere.
Keep going for the video, which really is worth a watch if you're even remotely into this. I liked all the testing he did.
Thanks to Jerry Y, who agrees is there anything you can't build out of LEGO?