Mysterious 'SSSS' Code On Your Boarding Card Before Flying?

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 via IFTTT