The "Quiet Skies" programme reportedly uses an unknown algorithm to flag flyers without any criminal record for surveillance on domestic flights.

According to TSA internal documents published by the Boston Globe, air marshals observe passengers for a number of behaviours including:

Excessive fidgeting
Excessive sweating
Cold penetrating stare
Wide open, staring eyes
Face touching
How much they sleep during a flight
Using a smartphone

it is the Right of the People to alter or to abolish it, and to institute new Government, laying its foundation on such principles and organizing its powers in such form, as to them shall seem most likely to effect their Safety and Happiness. Prudence, indeed, will dictate that Governments long established should not be changed for light and transient causes; and accordingly all experience hath shewn that mankind are more disposed to suffer, while evils are sufferable than to right themselves by abolishing the forms to which they are accustomed.

But when a long train of abuses and usurpations, pursuing invariably the same Object evinces a design to reduce them under absolute Despotism, it is their right, it is their duty, to throw off such Government, and to provide new Guards for their future security