A 16 year can fly without having to do anything other then buy a ticket and show up on time Same policies as an adult.
Mass transit generally has no age restrictions.
Disney transportation doesn't seem care if 16 year olds take Disney transportation to the parks
Posters are suggesting a young adult over 12 can fly without issues, can take Disney transportation without issues, can take public transportation without issues but needs special permission to ride an airport shuttle?
I don't agree with PP. I'd only be concerned if the child was under 12 ot if there was a posted policy on their website