Quite a few years ago (but after 9/11) I was with a group of RAF engineers touring the USA, visiting industry and USAF bases. Every single internal flight saw us all tagged for extra checking. We finally twigged that there was a code on the boarding cards.
It seemed our admin people had booked our transatlantic return flight as a separate booking so a group of men travelling the states with no apparent return ticket looked a tad suspicious.
After the first 2 internal flights we used to approach the scanner with our hands up, saying " xxxx endorsement on boarding card"