You might think it's just a boarding pass, but it possesses a lot of power.
From identifying the passenger to providing the flight number the boarding pass can produce a lot of information.
However, there is one code, "SSSS", that you don't want on your pass.
If you receive a boarding pass with the code SSSS (Secondary Security Screening Selectee) on it, you won't be able to print your boarding card off at an automated machine.
Instead, you have to check-in at the desk where you will be asked more thorough questions than other passengers and undergo less cursory perfunctory identity checks.
The boarding pass issued to the passenger will have letters "SSSS" written on it, and this means airport staff will be scrutinising the passenger at every checkpoint.
You will be given full body scans, a pat down and they will go through all luggage where you will be asked to turn on all electronic devices and have each item wiped down for explosive residue.
You've potentially raised some red flags with airport authorities.
Sometimes those picked to undergo an SSSS are chosen at random, but there are a few reasons why you could trigger an alert.
If you've paid for that flight in cash, that may also mean you now qualify, as can travelling from somewhere which is classified as a "high-risk country".
Also, if you're on a watch list then you will more than likely receive an SSSS code on your boarding pass.
After filling out a new form your boarding pass will be stamped and you'll be allowed on to the plane.
In April 2010, the New York Times found several children who were repeatedly selected for secondary screening, possibly because their names were similar to persons on the "No Fly" list.
Next time your pass has an SSSS code on it, make sure you give yourself an extra 30 minutes than normal to get through the airport otherwise you might soon be waving your plane goodbye.