The Transportation Security Administration (TSA) has begun collecting information on travelers through a program that monitors citizens not on a terror watch list or suspected of a crime, The Boston Globe reported.
The Globe reported Saturday that the program, titled Quiet Skies, aims to eliminate threats posed by unknown or partially known terrorists.
Undercover air marshals reportedly document passengers behavior, including whether they use technology when traveling, whether they change clothes at the airport, how closely they stand to the boarding area and other patterns.
TSA officials told the Globe that the agency works to deter potential terrorist attacks, but declined to address the Quiet Skies program.
Some air marshals told the newspaper that they view the program as a time-consuming and costly effort to track passengers who do not pose a threat.
The Quiet Skies initiative is separate from a TSA directive in May intended to address potential confrontations at airport security screenings.
TSA said it compiled a list of people who act suspiciously or confrontationally around airport checkpoints.
Individuals on the list go through a regular checkpoint screening process, the agency said. Their inclusion provides advance notice to TSA staff that an individual is scheduled to fly out of a particular airport.