Animated film maybe from the 80's or 90's about a boy on his bed that flies into another world? Maybe he saves a girl? I can't remember much more. Thanks.

Bedknobs and broomsticks? It's older than that, but I remember a flying bed in it.

Sigh, Little Nemo Adventures in Slumberland

Thanks a lot, this completes a missing memory of my childhood.

Yup, I would also say Little Nemo Adventures! :p Was a good movie :)