Originally Posted by corporate-wage-slave

ESTAs are checked digitally before boarding and via a regular batch job in the 72 hours before boarding. I think the advice is to use FNU with ESTAs, if she is eligible for one, but the reality of many people, more from India / Afghanistan, is that people double up their names and have other documents to support that. So at that point the gap kind of narrows between someone with one name, and someone with a duplicated same name.