Did you change clothes while at the airport? Get to the boarding area late? Fall asleep during the flight? Use your phone?

If you're on the Transportation Security Administration's new Quiet Skies list, then a federal air marshal knows the answer to all of those questions - and more.

Quiet Skies is a TSA domestic surveillance program that specifically targets travelers who are not under any kind of investigation or on a terrorist watch list.

The previously undisclosed program requires federal air marshals to follow ordinary US citizens through airports and on flights, documenting their every move.

Quiet Skies is a TSA domestic surveillance program that specifically targets travelers who are not under any kind of investigation or on a terrorist watch list

Federal air marshals must track everything about the person's behavior, referring to a lengthy checklist to make minute by minute observations.

Now some marshals are speaking out, telling the Boston Globe that they believe the Quiet Skies program is a costly waste of time that may even be unethical.

A TSA bulletin states that the purpose of Quiet Skies is to decrease threats by 'unknown or partially known terrorists and to identify and provide enhanced screening to higher risk travelers before they board aircraft'.

All US citizens are automatically screened for inclusion in the Quiet Skies program.

There are 15 rules to screening passengers for the program, with criteria including international travel patterns, behaviors that match those of known or suspected terrorists, or potential affiliations with someone on a watch list.

Passengers on the list have included a businesswoman who traveled to Turkey, a Southwest Airlines flight attendant, and even a fellow federal law enforcement officer.

The previously undisclosed TSA program requires federal air marshals to follow ordinary US citizens through airports and on flights, documenting their every move

While specific countries are not on any TSA bulletins regarding the program, air marshals revealed they were advised in several instances to follow passengers solely because they had traveled to Turkey.

When a passenger on the Quiet Skies list is selected for surveillance, a team of air marshals is placed on their next flight.

The marshals are given a file that contains a photo of the target as well as their basic information, including when and where they were born.

They then observe the target at length from the minute they get to the airport in one destination and leave it in another.

Marshals must note whether they were 'abnormally aware' of their surroundings, which could include reversing or changing directions in the airport, 'attempting to change appearances' by changing clothes or shaving on the plane, and boarding late or 'observing the boarding gate from afar'.

Behavior indicators that marshals must track are excessive fidgeting or perspiration, facial flushing, rapid eye blinking, strong body odor, sweaty palms, a 'cold penetrating stare', wide open staring eyes, face touching, and an 'Adam's apple jump'.

They must also note if the target's appearance has changed, including whether they've gained or lost weight, whether their hair length or style has changed, and if they've changed their facial hair.

General observations that are tracked include whether the target used a phone to talk or text, if they were in possession of a computer, did they check their baggage or take a carry-on, and if they used the bathroom.

Federal air marshals must track everything about the person's behavior, referring to a lengthy checklist to make minute by minute observations

Marshals must also know if the subject used public or private transportation to leave the airport after their flight.

Passengers can remain on the Quiet Skies list 'for up to 90 days or three encounters, whichever comes first', TSA documents state.

Thousands of Americans have already been tracked under the program and there are about 40 to 50 Quiet Skies passengers on domestic flights every day.

Around 35 of them are always being observed by air marshals.

Dozens of air marshals have expressed their concern with Quiet Skies since it launched in March.

Some marshals have gone as far as to seek legal counsel, fearing that the domestic surveillance program could be illegal.

Others believe the program is a waste of taxpayer dollars and only diverts time and resources away from legitimate threats.

The Air Marshal Association has also spoken out against the program.

'The Air Marshal Association believes that missions based on recognized intelligence, or in support of ongoing federal investigations, is the proper criteria for flight scheduling. Currently the Quiet Skies program does not meet the criteria we find acceptable,' it said in a statement.

'The American public would be better served if these [air marshals] were instead assigned to airport screening and check in areas so that active shooter events can be swiftly ended, and violations of federal crimes can be properly and consistently addressed.'

While TSA would not confirm that the program exists because releasing information would 'make passengers less safe', it did defend its use of federal air marshals on flights.

'FAMs may deploy on flights in furtherance of the TSA mission to ensure the safety and security of passengers, crewmembers, and aircraft throughout the aviation sector,' it said in a statement.

'As its assessment capabilities continue to enhance, FAMS leverages multiple internal and external intelligence sources in its deployment strategy.'