<When I was 18, I flew to Europe with my 15 year-old sister and we went around on a Eurail pass without staying regularly in touch with anyone>
That's exactly what my sister and I did for three months in 1967, except that we were 18 and 14. We lived through the experience. My daughter started flying by herself when she was 5 and my niece made several unaccompanied trips between Egypt and the US starting when she was 8. Some kids can do it with ease; some can't. I wouldn't criticize a 16-year-old who wasn't comfortable with the situation....I've seen many adults in a total panic at the idea of getting on a plane. After 9-11, there are many people who will probably never be able to bring themselves to fly again.