You won't need anything. A child that age just needs a parent or guardian. There is misinformation in this thread that has been reported.
I'm sorry.. But due to Trumps new policy, there is an age limit to passengers boarding flights now. You must be at least 16 years old to fly. If you have any further questions let me know.
Children usually don't need an ID, but it's a good idea to have their passport or a copy of their birth certificate just in case.
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