I don’t know how effective this is, but LEOs watching what people do in public isn’t anything new or worrisome.

Federal air marshals have been secretly tracking dozens of American travelerseach day who aren’t listed on government watch lists or suspected of a crime, The Boston Globe reported this weekend.

The Transportation Security Administration program, dubbed “Quiet Skies,” has existed since 2010 as an effort to mitigate the threat “posed by unknown or partially-known terrorists” after identifying people based on their travel history or other criteria. Air marshals then track such passengers and document their behavior at airports and in-flight, including how often they go to the bathroom, how many hours they sleep, if a traveler has “strong body odor” or “wide open, staring eyes.”

According to a bulletin issued by the agency in March and obtained by the Globe, the TSA tracks around 35 people every day. Which means thousands of Americans have been surveilled under the program since its inception.

Although some air marshals have criticized the program as expensive and ineffective, the TSA defended it in a statement to The Washington Post on Sunday, comparing the marshals to neighborhood law enforcement.

“We are no different than the cop on the corner who is placed there because there is an increased possibility that something might happen,” agency spokesman James Gregory told the Post. “When you’re in a tube at 30,000 feet … it makes sense to put someone there.”

“The program analyzes information on a passenger’s travel patterns while taking the whole picture into account,” Gregory added. “If that person does all that stuff, and the airplane lands safely and they move on, the behavior will be noted, but they will not be approached or apprehended,”