An avid traveler has revealed what 'SSSS' means on your boarding pass - and why you want to avoid it.

Chloe Jade Meltzer, 30, has been traveling the world since 2015 and has visited 162 countries.

Out of the hundreds of times she has traveled, Chloe has had 'SSSS' written on her boarding pass six times.

Those four letters stand for secondary security screening selection - meaning the passenger has been flagged for additional security checks by the Transportation Security Administration (TSA) before boarding the flight.

This means they will have to undergo additional screening procedures, including pat-downs, hand swabs, and thorough luggage checks before boarding the plan.

Chloe says one of the most common signs a traveller will have 'SSSS' appear on their boarding pass is if they don't get issued it immediately.

Chloe, a travel blogger, from New York City, said: "I have gotten 'SSSS' on my boarding pass periodically over the years."

"When I get one, I will just try get the checks out of the way and head straight to the boarding gate to be screened again by airline staff."

"Usually, how long it takes depends on how fast you get to the boarding gate, how your bags are packed and how fast they are at searching."

"When you are checking into your flight, you usually get your boarding pass. If you don't get it straight away, that can be a sign your pass will have 'SSSS' written on."

Chloe says if you are flagged for secondary screening you will be pulled aside at the gate before you board.

She said you will then either be given a pat down or a detailed search of your luggage - or you will be tested for explosives.

Chloe said: "You also might be asked a few extra question like where you're going and how long you're staying there."

"It can feel very targeted but usually this will be going on for a few other people as well or sometimes half the plane."

"I personally don't like this because it takes longer, you can't do this before boarding, they do it exactly at boarding."

Chloe said one reason you might have 'SSSS' is if you have traveled to certain countries that are flagged - indicating potential issues or alerts - or because you have bought a one-way ticket.

She says it is important not to panic when you get quadruple S on your boarding pass as it is issued randomly.

Chloe said: "They say it is randomly selected, sometimes it's because you have travelled to certain countries that are flagged, or because you bought a one-way ticket."

"Sometimes you might be on a watch list because you name is similar to one that they have flagged, or you have two different passports, you have passport irregularities."

"If you get the dreaded 'SSSS' don't worry, it doesn't mean you're in trouble because it is random."

"Just deal with it, be ready to board early and get it done."