Would you let your 15 year old fly alone and switch planes by themselve's?

Honestly it depends on your child. If I had a 15 year old who was responsible enough I wouldn't mind. But if I knew my 15 year old isn't mature enough to be out on his or her own, then no. So don't let others figure this out for you, work it out on your own. You know your daughter well, you can tell if she'll be able to manage on her own.