The Homeland Security Department wants to dig even further into the backgrounds of the 20 million overseas travelers who fly here every year — not by asking for more information about them, but by doing more with the data the U.S. already gets.
"This is an invaluable research tool for us, to be able to see if there's links from individuals of concern that we can find through these database systems," says Jayson Ahern with Customs and Border Protection.
While passenger names are now run against the terror watch list, Homeland Security wants to see where all kinds of data in an airline reservation leads.
The idea is to learn more, not just about the passenger who actually shows up at the airport, but also about such information as who paid for the ticket, using what credit card.
Beyond that, were cell phones found in searches of suspected terrorists used to book someone's flight?
Or did someone who lived at the address of a terror suspect pay for a passenger's ticket?
A former airline security director for American Airlines says it's essential to find out.
"When you really pool the various information that is available, all of a sudden you've got a picture," says Larry Wansley, now the CEO of Infinite Security. "It's simply like an evil jigsaw puzzle."
But privacy advocates say there are too few limits on how U.S. law enforcement agents would use such detailed information.
"It's not simply the planes that they're traveling on," says Marc Rotenberg, president of the Electronic Privacy Information Center. "It's the hotels that they're staying in, who they're traveling with. And under European law, that information is protected."
Now, U.S. officials say they believe the latest British terror plot is moving Europeans closer to agreeing that the data should be shared more widely.