The worst thing about a long-haul flight is, without doubt, the food. Forget turbulence, screaming toddlers or unexplained delays, meal times on a plane are almost universally unpleasant - and often stomach-churning - experiences.
At best, the food is edible. At worst, it's a scalding hot plastic tub of gloopy stew, overcooked rice or leathery meat and vegetables that have been boiled beyond all recognition.
Chef Gordon Ramsay is certainly no fan. He recently revealed he refuses to eat on planes, bringing his own spread to keep him going.
"I worked on airlines for ten years, so I know where this food's been and where it goes, and how long it took before it got on board," he said. Ramsay, it must be acknowledged, has a vested interest in knocking in-flight cuisine. His restaurant, Plane Food, based in Heathrow's Terminal 5, sells takeaway boxes designed to be eaten at 35,000ft. But is he right? Is it really all that bad? The Daily Mail reveals the unappetising truth about airline meals.
ROLL OUT THE READY MEALS - ONE BILLION EVERY YEAR
Whether you sit in first or cattle class, the food comes from the same place: an industrial kitchen near the airport, where it's cooked before take-off - then reheated on board.
In Europe, most meals come from Gate Gourmet in Switzerland or LSG Sky Chefs in Germany - serving more than 260 airlines.
Most of these industrial kitchens prepare around 25,000 meals a day; the world's biggest, the Emirates Flight Catering Centre in Dubai, makes up to 170,000. That's 58 million bread rolls, 4300 tons of chicken and 3.6 tons of lobster a year. Peter Jones, a retired professor of travel catering from Surrey University, says one billion airline meals are consumed annually in an industry worth £10 billion ($18 billion) a year.
"The challenge isn't the food,' he says, "it is getting the food and the other items on board. A jumbo jet needs 40,000 separate items loaded every flight, sometimes in 90 minutes."
DON'T BE FOOLED BY 'FRESH' - IT COULD BE 72 HOURS OLD
Despite stickers claiming it is "freshly prepared", most plane food is produced long before it is served to passengers. Usually, the meals are made between 12 and 72 hours in advance. But, adds Prof Jones: "It can be kept in a chilled stage for five days under the internationally recognised food hygiene standards."
Salads, desserts, bread rolls, plastic cutlery and napkins are put on trays in catering units on the ground and then stacked in trolleys ready to be wheeled down the cabin aisle.
Hot dishes are made in large industrial pans and decanted into plastic containers with foil lids before being 'blast chilled' to around 5C in 90 minutes.
They're then stacked in chilled metal boxes until they're taken on board the plane.
IF IT TASTES PLASTIC, THAT'S BECAUSE IT IS!
First class passengers like to think they're getting freshly cooked meals. But their food is also prepared on the ground, though it may be plated up in the first-class cabin.
Some chefs provide 'step-by-step' assembly instructions to help cabin crew present more intricate dishes - so even if the dishes come from the same place, at least they look more appealing.
There's also the benefit of metal knives and forks over the infamous plastic cutlery that is provided to economy passengers.
Not only is the latter very fiddly to use, but scientists have shown that it makes food taste worse - because of a phenomenon known as 'sensation transference', which converts a negative visual sensation into an unpleasant flavour.
Prof Charles Spence, an Oxford University psychologist and author of Gastrophysics: The New Science Of Eating, says: "We've shown that if you have heavy cutlery you rate food better and will pay more. Plastic takes you down by ten per cent."
CHOOSE THE STEW (AND AVOID PASTA)
There's only one way to ensure your food isn't dried out and disgusting: choose the sauciest option. Stews, soups or casseroles always taste best on board.
French chef Raymond Oliver is credited with coming up with the 'wetter is better' theory in 1973, when he created beef bourguignon, coq au vin and veal in cream sauce as the three staple dishes for a new French airline. The meals were a roaring success and soon began to appear on all European planes.
Stew is a safe choice because it's packed full of umami - a meaty, savoury flavour - which compensates for the blandness of most on-board meals.
"You often have dishes with tomato, parmesan or mushrooms; this allows you to make food tastier without adding too much salt," explains Prof Spence.
On the other hand, pasta, noodle and rice-based dishes are best avoided. They don't hold their texture when reheated. "It just goes into a big lump," says James Griffith, assistant vice-president at Emirates Flight Catering. Another no-no is fried food, which turns soggy and flavourless when heated for a second time.
BRING YOUR OWN SALT AND PEPPER
Conditions inside the plane dull our senses and make food and drink seem blander than normal.
Prof Barry Smith, of the Centre For The Study Of Senses at University of London, says: "The environment of an aircraft is about the most hostile to having a good dining experience that you could imagine."
At 30,000 ft, humidity is less than 12 per cent: drier than most deserts. This dehydrates our nose, making it harder to smell food and appreciate its flavour, while low air pressure numbs our tastebuds.
A 2010 study at the Fraunhofer Institute For Building Physics showed our perception of saltiness falls by up to 30 per cent on a plane, while our sense of sweetness plummets by 20 per cent.
So even if a dish is perfectly cooked and seasoned on the ground, in the air it could be tasteless - meaning those little sachets of salt, pepper and even tabasco sauce could come in handy.
Airline chefs compensate by adding hot spices such as chilli and wasabi. We detect the kick from spicy food through the trigeminal nerve in the nose, which is unaffected by flying.
A NICE CUPPA? SORRY, NOT AT THIS ALTITUDE
The low cabin pressure means water boils at 90C, not the usual 100C, resulting in a poor cup of tea. Meanwhile, passengers' dry sinuses can alter the taste of coffee.
There's also the matter of the water. Aircraft coffee isn't always made with bottled water; rather, the drinking water on board a plane, which - though clean - is far from high quality.
Short layovers mean there is little time to clean the valves in the pipes, resulting in a build-up of minerals and grit.
Some airlines have compensated by coming up with different blends of our favourite hot drinks.
Singapore Airlines created a special plane coffee (with more flavoursome Robusta beans than the usual Arabica blend); while Twinings designed a 'high tea' which is intended to taste good when brewed at a lower temperature.
HESTON'S PIE IS A FREQUENT FLYER
Some airlines offer truly world-class cuisine, by partnering with celebrity chefs who help devise their menus - and have strict instructions for how they should be prepared, cooked and served.
Virgin Atlantic contracted model-turned-chef Lorraine Pascale to come up with Thai beef salad and chilli con carne, while Heston Blumenthal's collaboration with British Airways involved shepherd's pie with a seaweed crust.
The involvement of high-profile chefs has led to increased control over the ingredients and presentation of the food.
Strict regulations on the weight capacity of planes means there is also much scrutiny over recipes, which are astonishingly exact - even in economy.
Ingredients - right down to the sprinkle of flat-leaf parsley on top of a tomato consommé - are measured out to a hundredth of a gram. This can help companies save vast sums of money, too. In the Eighties, American Airlines realised it could save £31,000 ($56,000) a year by removing a single olive from each passenger's salad.
IT'S A BAD IDEA TO WHINE AND DINE
The noise of a whirring jumbo jet engine - which can reach an ear-splitting 85 decibels - can ruin a good meal. This is because it's akin to white noise - random collections of sounds at different frequencies - which is distracting to the human brain and diminishes our sense of taste.
Prof Spence explains: "Background noise suppresses the ability to taste sweet and salty, but enhances the ability to taste umami, the meaty, savoury taste you find in food such as tomatoes. It's been shown that a large number of people only drink Bloody Marys, made from vodka, tomatoes and Worcestershire sauce, when flying."
Experts advise listening to soothing music or using sound-cancelling headphones to counteract the engine's dulling effect.
In 2014, BA devised a music menu to be enjoyed alongside its meals on long-haul flights, including Debussy's Clair De Lune paired with roast dinner and Scottish singer Paolo Nutini with a smoked salmon starter.
CHOCS AWAY, BUT DON'T LET IT MELT
As ANYONE who's ever tucked into a chilled, cardboard-like cake on a plane can attest, airline chefs tend to prioritise practicality over taste when it comes to your onboard dessert. Chocolate is almost always used because it acts like a glue, keeping layers of pastry, cake or mousse together and stopping them from disintegrating before take-off.
The only problem is its tendency to melt when placed beside the hot main course, meaning all the desserts are chilled before they're served to passengers.
Scientists don't know why, but sophisticated seasonings such as cardamom, ginger and cinnamon taste even more intense in the sky, so these are often found in plane puddings.
TAKE A TIPPLE BEFORE YOUR TASTEBUDS DRY
Wines that taste amazing on the ground can lose all their flavour mid-flight. Subtle fruit flavours are diminished and drinkers are left with bitter tannins.
This is because the liquid thins out and becomes leaner in the air, in response to changing atmospheric pressure. As a result, most airlines serve younger, fruitier reds over light whites.
Prof Smith says the best wines on board are those grown on mountains, such as Argentinian Malbec, produced at 5,500ft, where air pressure is close to that found in aircraft cabins.
Even better, however, are sparkling drinks.
"Champagne is a winner because it has a flavour delivery system of its own," says Prof Smith.
"The bubbles rise in the mouth and nose and are coated with liquid so they deliver the odour and flavour."
Whatever your tipple, experts advise drinking it early in the flight (before your tastebuds dry out) and not indulging too much.
Low air pressure has been shown to thin the blood, meaning the concentration of alcohol in our body - and its effects - can be stronger on a plane.
GIVE THAT FOLDING TRAY A GOOD WIPING
Food poisoning incidents on planes are rare. But, just in case, caterers keep a sample of every meal cooked to check later if there are complaints.
And pilots and co-pilots are served different foods, to avoid the risk of the entire cockpit falling ill.
Whenever you fly, hygiene experts advise bringing disinfectant wipes on board. Fold-down trays are thought to be the dirtiest surfaces on a plane, with more bacteria than a toilet seat.
Former airline worker Allison Hope last year warned against putting food down on your tray. "Sadly, they are cleaned far less than you'd be comforted to know," she revealed.
AND YOU'LL END UP FEELING SWELL . . .
The low pressure makes your body swell - noticeably the feet, but also your internal organs. Engorged intestines struggle to digest food, so you feel bloated.
Nutritionists recommend foods that require the least amount of oxygen to digest: carbohydrates such as potatoes, beans and nuts.
The average plane meal is far from healthy, with around 360-400 calories per food item (so roughly 1,500 calories total) and high quantities of fat, salt and sugar.
Prof Jones says: "Airlines are not hugely concerned about nutrition because their view is that one meal consumed by a passenger will not make the slightest bit of difference to them out of the thousands of meals they consume."