My daughter, who resides in the US, is about to fly to the UK for a brief trip. She holds both US and UK passports and citizenships, and has a NEXUS card.
Now, just before departure, we have realized that her US passport is inaccessible (it is with a distant relative).
Can she instead travel on her UK passport, then on her return successfully enter the US by presenting the UK passport, her US birth certificate and her NEXUS card? (I'm guessing they would be pretty unhappy, but not prevent her entering since it's clear she's a citizen.)
Assuming they will let her in, will she have any trouble leaving the country in the first place - given that the airline has her US passport number attached to her ticket?