What 80's movie is this?

I remember a movie that I used to watch when I was a kid but I cant find it anywhere and I dont know what it was called. The plot is that a boy gets abducted by aliens for many years but doesnt remember a thing. then, he gets put back where they abducted him but he hasnt aged at all, his little brother is now older than him and scientists do tests on him. he then rides around in a spaceship. Please help me identify this movie!