Now that the world has opened back up, many of us will be planning on jetting off somewhere for an adventure or relaxing break very soon.
But if you're going on holiday to the US especially, you might want to keep a close eye out on your boarding pass.
As reported by The Daily Record, a travel expert has shared four letters to look out for on the pass and a warning that goes along with them.
Posting on TikTok, a woman named Michelle G, who shares luxury travel tips, explained what it means if you have the letters 'SSSS' on your boarding pass at security.
Get the news you want straight to your inbox. Sign up for a Mirror newsletter here.
Michelle, from the US, who posts under @laxtoluxury, said: "This is something you never want to see on your boarding pass - the quadruple S.
"It stands for Secondary Security Screening Selection and means you're going to get searched again super thoroughly and is usually on international flights to the US."
Getting the code stamped on your pass overrides any pre-approval through a Trusted Traveler Program and can add up to 45 minutes (or more) to the boarding process.
While most people who get the stamp are randomly picked, Frank Harrison, regional security director for North America and the U.K. at World Travel Protection told Conde Nast Traveller that there are a few factors that can unknowingly get you flagged for the security screening.
He explained: "Many travellers unknowingly flag themselves due to inconsistent but innocuous travel behaviours such as booking a last-minute ticket or paying in cash. If you exhibit behaviour that is inconsistent with your profile—say, for example, suddenly adopting a jet-setting pattern—this is a red flag and a potential alert for drug or human trafficking. Consistency is king."
Some travellers might also be marked as SSSS for booking one-way tickets, flying through countries deemed 'high risk' by the State Department or if your name happens to be similar to someone on a Department of Homeland Security watch list.
If you find yourself constantly getting the quadruple S stamp on your boarding pass, there is one thing you can do to try and make it stop.
In another TikTok video, Michelle adds: "If you go to the US Department of Homeland Security website, you can apply for a redress number which prompts the DHS to review your record and clear up any erroneous or weird info that could be triggering the additional security measures.
"Once they’ve investigated your records and you’re hopefully cleared, you’ll want to input your redress number on all of your flight reservations going forward, and you should hopefully be good to go.
"If you only get it once or very seldomly, you could’ve been randomly picked. This is for people who get it repeatedly (so it’s not random!)"
Do you have a story to share? We want to hear all about it. Email us at yourmirror@mirror.co.uk
