Upvote:2
These regulations are in place to stop interference with custody orders, and I suppose runaways although that is a little hard to worry about for an airfare. A 17-year-old who can answer questions about his home life and travel plans is a small risk. I think a witnessed letter would be ample. My younger child was never asked anything at all, although he was armed with a US Notarized letter.
Upvote:3
thanks for your feedback, he has a US and UK passport.
In the meantime I've had a reply from CPB:
Thank you for contacting U.S. Customs and Border Protectionβs (CBP) Information Center.
CBP strongly recommends that unless a child is accompanied by both parents, provide a letter which states you are giving him permission to travel by himself internationally. Letter from the child's other parent or parents stating: "I acknowledge that my son/daughter is traveling out of the country . He/She has/have my permission to do soβ. The letter should include Who, What, Where, When, Why, and contact information for the absent parent(s). Having the letter notarized is not necessary but is highly recommended.