What 'SSSS' means and why you don't want to see it on your boarding pass

However, if your boarding card contains the letters 'SSSS' on them then it will take passengers even longer to get on their plane.

The message means that airline passengers have been selected for a Secondary Security Screening which means they face extra security checks.

'SSSS' stands for Second Security Screening Selection and means that you won't be able to print your boarding card out at home or from an airport kiosk.

It means you'll have to get your pass from the desk and face extra bag searches, pat downs and identity validation all conducted by the Transportation Security Administration.

The number of names on the list is guarded in secrecy but it is thought there are tens of thousands of names on the list.

There is no published criteria about what may get you on the list but some criteria include passengers with a one-way reservation or those who have paid for their tickets in cash.

Lifehacker.com also states that last-minute flights and travelling to a 'high-risk country' could also put you on the list, as well as being randomly selected.

They state that the whole experience can take between 10-30 minutes so advice passengers to get to the airport extra early for the flight.

Anyone who fails to take part in this enhanced security screening, if selected, will result in them being denied boarding.