Originally Posted by
Bogwoppit
Sadly it is "under 12", not 12 and under. Your niece is not exempt.
For domestic travel, how will the TSA know if someone is under 12 years of age or is 12 years of age? Asking won't always give them the answer they want.
If I were once again an enterprising 11 year old, I would hang out at airports and use my miles for refundable tickets to go airside with passengers wanting a companion to skip part of the TSA's junk checks.