Requirement to provide passport info 72 hours before flying to USA
I'm a US citizen, I book a lot of flights to the US. The airline website often has prompts to enter passport details and says these must be entered 72 hours before the flight.
What happens if someone doesn't do it? Are people, including US citizens, being barred from travel to the USA when they arrive at the airport because they didn't enter their passport details 72 hours in advance?