Information on a US surveillance program targeting persons not known to be terrorists has been leaked (archived). The progam dubbed "Quiet Skies" involves the assignment of air marshall details to follow travelers who meet the following criteria:
- Not under investigation by any agency
- Not in the terrorist screening database
Selected targets are then followed by a team of armed plainclothes air marshalls for the duration of their US air travel. In their report on the program, the Boston Globe estimated the program manages to handle 35 targets daily.