Reply #8: I think the TSA rules require minors to have approval from an adult ot fly

[rpannier]

I think it's one of those post 9/11 restrictions. I have two daughters and when they fly to visit their grandparents Korea to the US, they must have an adult present at the ticket counter with them to show they can get on the plane.
An addition:
Anyone under age 17 who is flying alone on an international flight must have a signed note from a parent or responsible adult giving permission, destination and length of stay.

Minors must be met at the destination by another parent or responsible adult.


source:
http://www.independenttraveler.com/resources/article.cfm?AID=203&category=11