There are plenty of reasons flying is stressful, but one of the biggest headaches of modern air travel is the security procedures. Who knows what fresh nightmares the TSA will have cooked up for you by the time you hit the terminal?

Well, there’s at least one hint you can use to determine whether or not you’ll be spending a little more time in the security area on your way to your gate, and it has nothing to do with that bottle of water you’re carrying. As both Refinery29 and Business Insider have reported, there's a four-letter code at the bottom of your boarding pass that can tell you whether you'll be pulled aside for extra screening.

If you see the letters “SSSS” at the bottom of your ticket, you’re in for a little extra attention at the security checkpoint. To compound the headache, you won’t be able to print your boarding pass at home, and will have to get it when you arrive at the airport.

If you’re predestined by the airport gods (also known as the TSA’s Secure Flight program) for Secondary Security Screening Selection, you’ll get an “enhanced screening,” which means you might get some extra questioning or be subjected to a pat-down, body scan, or luggage search.

While some passengers are chosen for extra screening at random, the TSA also flags people based on what they call “risk-based, intelligence-driven information." The so-called “selectee” list, a less strict version of the No-Fly list, is maintained by the FBI’s counterterrorism unit. Being on the list can be a huge pain: The ACLU reports [PDF] that people on the Selectee list “can be subjected to delays, humiliation, and improper questioning about the First Amendment-protected beliefs and associations—no matter how many times they have been through such screening and cleared security.”

As One Mile at a Time credit card blogger Ben "Lucky" Schlappig, who flies frequently and has been subjected to the process, explains it, it usually takes about 10 to 20 minutes of extra time in the security line to pass through the enhanced screening. Many people who receive extra screening believe it’s due to traveling to places that look suspicious to the government, as in the case of a travel blogger whose frequent flier points took him on a confusingly circuitous trip through Turkey. Even though he was already a member of TSA’s Global Entry background check program, he still seemed to have ended up on a watchlist. (That said, it's very difficult to figure out if you're on one of these lists and why, so it's hard to say for sure why you might get flagged regularly.)

But if you only receive the SSSS code once, you probably don’t have to worry about being on any sort of list. You may just have been selected at random. Lucky you.

[h/t Refinery29]