Security is getting stricter and stricter in airports all around the world. They go through our bags with a fine-toothed comb, weigh our luggage to make sure they don’t exceed the weight limit before we then also have to go through metal detectors… But you might get a double check... SSSS. If your boarding pass is marked with these four letters, you're going to spend a lot of time going through airport security. They can be printed or written by hand.The dreaded letters in question.These mysterious letters actually mean 'Secondary Security Screening Selectee.' If you're selected, you'll have to go through a second security check, or you'll be asked a few questions, and will have to undergo a more detailed identity check.You can also expect your suitcase and electronics to be searched. All of this can take more than 30 minutes. To find out if you've been selected, all you need to do is check-in online and print your boarding pass at home. If you can't, however, you should try to get to the airport a little earlier.This selection can also be made at random, at the airport, before you board the plane.