Why you never want to have this code on your boarding pass

Airline passengers who find 'SSSS' stamped on their boarding passes will face extra security checks and delays, it has been revealed.

This is because the innocuous looking code, which applies to travellers flying into the United States, stands for 'Secondary Security Screening Selection'. 

It means the pass holder has been selected to undergo a more extensive security screening process before boarding their flight that can take up to half an hour. 

The screening process, which may include bag searches, pat downs and validating identity, is conducted by the Transportation Security Administration.

The TSA insists travellers who receive the 'SSSS' are selected at random, but some have claimed they are pulled aside most times they travel, according to Lifehacker.

Buying one-way tickets or paying in cash could land passengers on the TSA's secret list and lead to frequent 'SSSS' checks, the publication said.

A passenger may be able to tell they will have to undergo additional checks if they are unable to print their boarding pass at the airport's self-check-in. 

According to Seth Weinstein, a U.S. customs attorney, the Department of Homeland Security and and Customs and Border Protection use the Terrorist Screening Database maintained by the Terrorist Screening Center to determine who qualifies for Secondary Security Screening Selection. 

Failure to take part in the enhanced security screening will result in the traveler being denied boarding.

The scheme was introduced after the 9/11 terror attacks, to help security officials monitor potentially dangerous individuals from entering or leaving the U.S. 

But travelers can request to be removed from the Secondary Security Screening Selection List by submitting documentation and evidence to the Traveller Redress Inquiry Program. 

This article was first published on dailymail.co.uk and is reproduced here with permission.