I was on a flight sitting in 1a on a 737 or something similar and a 8ish kid walked on sat in 1b and that was that. Maybe he had an adult in the cabin nobody asked about moving and he never acknowledged anyone else near by for the 3ish hour flight. He was no bother to me except I opened his snack basket stuff for him. The first time it came through he tried to clean it out. :-)