I haven't yet I've just done the research and reserved his tickets for this December when we're going to Italy to visit my family. It will be his first time on a plane, but he usually travels well and just plays with his toy on my lap or sleeps. So hopefully he will behave on the plane too
Technically, your baby is supposed to remain in his/her carrier during the entire flight. If you're lucky and get nice flight attendants they may let you take your baby out or pretend not to notice if you take your little one out to stretch or cuddle on your lap for a bit. The bathroom tip seems like something you may want to try and will probably be easier if your baby is pad trained
If you have any breaks at airports you should take your baby to the bathroom as well and let her walk around a bit. Don't forget to take some nutri-cal with you.
Desiree & Eros