A kid can solo in a sailplane (glider to laypeople) at age 14. He/she can get a sailplane pilot's license at 16. A kid can solo in a powered plane at 16 and get a private pilot's license at 17. Higher licenses have higher age limits, but if I'm not mistaken, even the highest Airline Transport Pilot license can be earned at age 21.

Age really has little to do with it. The bigger question is maturity. I know a man who was flying B-17 bombers in combat at age 19. He enlisted in the Army Air Corps at age 17 in 1943, went through Basic, Gunnery, and Radio Operator school before getting into pilot school. He graduated pilot training at age 18, went through his B-17 training over the next few months, and reported to England to fly in the 8th Air Force shortly after his 19th birthday. He was flying an armed bomber just 50 feet or so away from other planes with a crew of 8 or 9 other young men while people were shooting at them. Within a few months, he was selected to be the 91st Bomb Group's Combat Check Pilot in charge of training new crews in aerial combat. He'd gone from Buck Private to holding a Major's position in 19 months. Like I said, it's more a question of ability and maturity than age.