My parents sent both me and my sister on planes by ourselves several times when we where kids (in Europe). Now this was a good 25 years ago, but then it seemed like a perfectly normal thing to do and there where often two or three other kids flying unaccompanied and the airlines and great routines for handling it. Basically we'd be assigned a staff member who would follow us from check-in until we where seated on the plane, and then there would be another staff member that met us on the plane when we landed and followed us out to the arrivals hall and made sure we where met by someone.

Until right now I never even reflected over that anyone would find this strange or abnormal.