Yes. She doesn't need an ID until she's 18. I just flew yesterday from MSP to IAD with my friend who is 16, and he didn't need an ID.
A notarized letter from the legal guardian(s) may be sufficient to authorize the uncle to travel with his niece.
does he have her birth certificate?Also have her parents write a letter with permission to fly with him and have it notarized. also if possible take her for I'D from the court house
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