Preparing to travel by aeroplane can often prove a stressful experience: you have to cram everything you need into your suitcase (and then some). You need your boarding pass, passport and any other paperwork prepped and ready. You have to decant liquids into tiny bottles and set them aside in a plastic bag. And, if you’re a nervous flyer, you’ve additionally got to haul on anything and everything you need to keep yourself feeling calm, relaxed and able to handle the (air) pressure.

The most annoying of all, though, is having to get to the airport hours before your flight to check in and get through security – ideally without being pulled off to one side because the underwire in your bra set off the metal detector.

However, if you want to know if your time being patted down, scanned and having your bag searched is going to take longer than usual, all you have to do is look down at your boarding pass to see if it has been branded with this particular stamp:

The ‘SSSS’ on your boarding pass stands for “Secondary Security Screening Selection”, and it is every bit as fun as it sounds (read: not at all fun).

They are put through a more intensive screening process, which “may include enhanced pat-downs”.

According to a document on security processes leaked in 2009, it is also likely that “carry-on luggage may also be inspected by hand, [and], in the case of film or other items that cannot be X-rayed, the agent may perform a test for possible explosive materials.

“The screener may also use a handheld metal detector to search the passenger for metal objects.”

Read more: These shocking 21st century adverts are a grim reminder that sexism is alive and well

The acronym is used as an airport security measure in the USA, which helps them to select passengers for additional inspection – and a lot of British passengers, in particular, have complained about receiving the stamp multiple times when travelling to the States.

According to Metro, receiving an ‘SSSS’ boarding pass often prevents you from accessing the pass from your phone, which means that you need to print it from a kiosk at the airport or get it from an agent. 

Read more: Your Fat Friend wants you to know what it’s really like to fly as “a very fat person”

Neither the Transportation Security Administration (TSA) nor the airlines publish the criteria issued to identify passengers who will be given extra screening or be denied boarding.

It is thought, though, that passengers with a one-way reservation or who pay cash for their tickets are more likely to receive the ‘SSSS’ stamp.

The Selectee list has been condemned by civil liberties groups as infringing on privacy rights and potentially leading to racial and ethnic discrimination.

However, security officials insist the move will allow them to trace potentially dangerous individuals from entering or leaving the USA. And, if you've seen the code pop up on your boarding pass more than a couple of times, you can contact the TSA and appeal the decision to have you placed on the list. 

Image: Margo Brodowicz