But legal experts slammed the program.
"They haven't demonstrated any need for it or whether it's effective," said Faiza Patel, co-director of the Brennan Center’s Liberty and National Security Program, noting that the TSA has yet to reveal whether "Quiet Skies" has stopped any security threats. "We certainly need to have more information, but I think the concerns that they are profiling are pretty high."
Patel said every aspect of the program poses concerns: how the TSA chooses which passengers to track; what data the TSA is collecting; and then what becomes of the data. Keeping such information may be a violation of the Privacy Act, a federal law that governs how personal identifiers are collected and used.
"As far as I know, this data collection hasn't been specifically authorized by Congress, and even if it was, they would have to publish a notice that they're collecting this information and keeping it in a database — which we haven't seen at all," she said.
"Quiet Skies" also raises questions of whether the TSA has continued to use passenger-screening methods that were discredited more than a year ago.
Last February, the American Civil Liberties Union criticized another behavior detection program that the TSA had been using to flag certain travelers for additional inspection, finding it to be unscientific and rife with racial and religious profiling.
Handeyside balked at the behavior checklist reportedly being used for "Quiet Skies," which includes observing things like a "jump" in a man's Adam apple or being "abnormally aware of surroundings."
"A lot of those behaviors reflect what may be consistent with stress or anxiety, and if they're looking for stress or anxiety in an airport, they'll find it," he said.
The surveillance has also received criticism from within the TSA, according to the Globe, which reported that multiple unnamed air marshals felt the work was time-consuming, costly and a distraction from more important law enforcement work.
John Casaretti, president of the Air Marshal Association, the federal air marshals' union, echoed that.
"The American public would be better served if these [marshals] were instead assigned to airport screening and check-in areas so that active shooter events can be swiftly ended," he said in a statement.