Did my first solo flight at the age of 13. Not as a UM, straight up normal ticket. Dad drove me to the airport, I managed myself from there. Sent my daughter off on her first solo flight when she was 14, dropped her off at the airport and she handled herself from there. Daughter later remarked she much preferred flying along than with me or her mum, as she had total control over the pace, what to eat and drink, and where to hang out. I think she inherited that from me.