Each and every time you board a plane, it can sometimes seem as though the flight attendants and pilots are communicating in an entirely different language. Whether barking codes to each other over the loudspeaker or simply relaying news in difficult-to-understand abbreviations, it's not uncommon for passengers to wonder just what exactly is going on. Now British Airways Senior First Officer, Mark Vanhoenacker, has spoken to MailOnline Travel to reveal the most unusual jargon used on flights, and what it really means... British Airways Senior First Officer and author, Mark Vanhoenacker, shares the strangest in-flight jargon . The Heavy . 'This isn't a reference to my waistline!' Vanhoenacker tells MailOnline Travel. 'British Airways will always have tow pilots flying at any one time, but will have three and sometimes four pilots on its long-haul services, such as those flights to Singapore or Buenos Aires. 'The heavy pilot takes turns flying, allowing one of the other pilots to take a break.' The en-suite fleet . 'This is an affectionate term for the 747 fleet,' he explains. 'The 747 has not just a very cosy bunk in which to take our breaks - on flights with heavy crew, that is - but also has a toilet inside the cockpit.' Positioning refers to when crew members travel as passengers, often when a route is switching upon arrival . Positioning . 'This occurs when crew members travel as passengers,' Vanhoenacker reveals. Often it happens when 'a route is switching to a new aircraft type and a crew must already be in place overseas to bring the first flight home.' 'It has a more colourful name in North America: deadheading. 'To remember, just think Frank Abagnale Jr. and the film Catch Me If You Can.' There-and-backs are routes that allow the crew to make it back home - to London - in time for dinner . There-and-back . 'It sounds like something Tolkien would have written about, but for an air crew, it refers to a trip that runs from home - London  to a city like Rome or Stockholm and then back on the same day. 'There-and-backs are always popular,' he adds. 'We may even land in time for dinner! 'If we do have to stay the night in a hotel, it's called a nightstop.' Every airline has their own call-sign, and for British Airways, all aircraft identify themselves as 'speedbirds' Speedbird . 'Every airline has its own call-sign, which consists of a name followed by a version of the flight number,' Vanhoenacker explains. 'For many airlines, the call-sign is simply the name of the airline, but the British Airways call-sign is 'speedbird,' a name with plenty of history behind it. 'For example then, British Airways flight 117 from Heathrow to New York will identify itself on the radio as Speedbird 117.' Pilots often refer to air traffic controllers who align and space out arriving jets at a busy airport as 'Directors' Yes, they have a few oft-used phrases, too. Slam-click(er) Air stewardess Sarah Steeger, who works for a US carrier, explains that this is when a crew member goes to the hotel and does not emerge again until it’s time to leave. As in: slamming the door and clicking the lock. End of story. Can be used as a noun or a verb. ('I’m so tired I’m just gonna slam-click.' or 'You won’t see her for dinner. She’s a slam-clicker. )’ Pink eye . Similar to a red eye flight, a pink eye is just short of a long-haul overnight journey. A red eye is a flight that touches the 1 am hour, according to flight attendant, Blissom Booblé, so a flight that goes to midnight would be a pink eye. Coach roach . Used wryly, usually for flight attendants who prefer working in the main/coach cabin. 'Business? No thanks. I’m a coach roach all the way, baby!' Crotch watch . Nickname for walking through the cabin to do a seatbelt check. Also called a 'groin scan'. The Director . No, it's not the name of an upcoming Arnold Schwarzenegger film, it's the term applied to certain air traffic controllers. 'Those who align and space out arriving jets at a busy airport are called directors,' he says. 'When pilots, landing at Heathrow for example, hear that it's time to contact the Heathrow director, it's a sign that one of the most finely choreographed parts of the flight is about to begin.' The Sin Bin . 'This is the area of the taxiways near a runway where an aircraft may be sent to wait - out of the way of other aircraft. 'Typically, it occurs if a flight has a time restriction on its departure, either because its direction of flight is busier than that of other aircraft or because there's inclement weather at its destination.' Moral of the story? When you hear this term, you may want to send a quick text to let your loved ones know you'll be landing late. Pilots often make reference to the jets, which is the streaming quality of the air, when looking at weather charts . The jets . You may think that this is in reference to the gigantic planes that the pilots are captaining, but it's actually in reference to jet streams: the very high, fast winds that speed or impede the aircraft's journey. 'The 'jet' in jet stream comes from the streaming quality of the air, not the aircraft we most associate with them,' Vanhoenacker explains. 'Though it is a pleasing coincidence. 'I might ask where the jets are this morning while looking at a weather chart or in flight we may comment on how strong the jets are.' Often, the airline staff is required to report the total number of customers and crew, called souls on board . Souls on board . 'When we operate at certain airports, we're required to report the total number of customers and crew on the aircraft,' he adds. 'We call this souls on board.' 'In aviation, which has so much new terminology and technological jargon, this is one of those pleasing phrases that sounds all but antique.' Essentially, this a fancy name for the plane's head count. Senior First Office Mark Vanhoenacker is also the author of the upcoming book, Skyfaring: A Journey with a Pilot, which will be available in stores and online on April 2.
Pilots and flight attendants use some strange sayings while on board . Most commonly used include: The Heavy, The Sin Bin and there-and-backs . Senior First Officer, Mark Vanhoenacker, explains the odd phrasings .