Cruising 40,000 feet in the air can be stressful at the best of times, but there is one thing you never want to hear.
Picture this: you're halfway into a four-hour flight sitting in economy on a budget airline, the person to the right of you has long, dangly legs poking onto your side, while the person on your left is overflowing onto your seat.
Your phone died before getting on the flight as you couldn't find a plug socket at the airport, and you've spent your last few pounds so you can't afford to buy any refreshments or food on the trolley - you're accidentally raw-dogging the entire flight.
Advert
Could things get any worse? Unfortunately...they can and they do.
You hear the tannoy go off and the pilot calmly says 'could a CSD report to the flight deck immediately' - s***'s just got real.
We'll get into what it all means momentarily, but that could be the last thing you'd ever want to hear on a commercial flight.
A British flight attendant revealed the nine-word secret message to Express.co.uk, and explained that CSD is lingo used throughout the aviation industry and is an acronym that stands for 'Cabin Service Director'.
Advert
Speaking to the publication anonymously, to protect her from being fired from the airline she works for, she said: “A scary code for the crew would be - ‘could a CSD (Cabin Service Director) report to the flight deck immediately’ or 'could a senior member of crew report to the deck'.
"It's a call made by the captain or the first officer - depending on the situation. And this could mean a number of things.
“It could be a medical emergency up in the flight deck, it could be that we’re going to have a tough landing. Or It could be something more sinister... like we’ve gotten a call, that something on the plane."
Advert
The air hostess added: "It basically means there’s an emergency and we need to talk to someone.”
For those of you that may be thinking 'why don't they just say what's up to everyone on board', well it would just create a sense of panic among the passengers - who wouldn't be able to do anything to alleviate whatever issue arose.
Unless the issue was snakes on a plane and Samuel L. Jackson was onboard dropping mother F bombs.
Advert
Explaining why airlines use the secret code only known among staff, the flight attendant added: "The flight crew do not have time to be kind of calling around every door to find out where the manager of the crew is, and that they just need them in there right now."
But it is definitely not something travellers need to worry about, as crews are trained for every scenario, and the likelihood of a plane crash in the US - or most other countries for that matter - is incredibly rare.
Harvard University published a study in 2017, where researchers claimed that the odds of your plane crashing are one in 1.2 million - and the chances of dying in a plane crash are one in 11 million.