Small symptoms (weeping over a missing fork in your dinner service, or a reduced ability to turn off a succession of Vin Diesel movies) are often indicators of larger health issues screaming “Ta da!” behind the scenes, but you can stay fit and happy by asking the following questions.

THE SEVEN RULES OF FLYING I LIVE BY

BEST FIRST QUESTION ON A PLANE EVER

FLIGHT ATTENDANTS’ SECRET TO BEATING JET LAG

THE SECRET TO SLEEPING ON A PLANE

WHY DO I BECOME SO GASSY?

No, it’s not that quick lunch you grabbed on your way to the airport; according to one study by the University of Copenhagen, flatulence increases significantly in the air thanks simply to physics which sees cabin pressure drop as flights climb, leading trapped gas within our bodies to expand accordingly. (Interesting fact: a 1969 study highlighted the risk of a fireball arising from astronauts’ wind, held in high concentration within the confines of the spaceship).

While expelling gas as frequently as you can in the bathroom is recommended (holding it in causes pain and further bloating), Steven Reed, an industrial officer of the Flight Attendants’ Association of Australia, says flight crew prepare for flights by eating light meals, exercising before and after a flight and taking medication to assist with swelling and flatulence. “Above all, it’s about avoiding foods likely to cause gas, staying hydrated and remaining active to keep gas from settling.”

WHY DO MY LEGS SWELL WHEN I FLY?

If you’re struggling to put on your shoes at the end of a flight, there’s every chance you’ve spent too much time sitting in the one position for hours at a time – a nasty habit which restricts blood flow throughout the body and leads to swelling of the feet and ankles in particular.

It also adds to your risk of developing Deep Vein Thrombosis (DVT), a potentially fatal blood clot which can form when blood isn’t circulating freely.

Reed says while the best defence against swelling and DVT is to take regular walks to the bathroom and back, he acknowledges it isn’t always possible when the meal carts are out.

“That’s why I always advise travellers to read, and follow, the simple exercises, (instructions for) which can be found in the back of every in-flight magazine,” he says.

Those who are at increased risk of developing DVT should speak with their GP before flying.

WHY DOES MY SKIN FEEL SO DRY AND TIGHT?

If you’ve ever wondered why you’ve stepped onto a plane looking dewy and youthful and stepped off … significantly less so.

Reed recommends boarding a long-distance flight with an unpeeled orange in your bag. “You’ll notice that over the course of the flight, the orange will shrink and shrivel until it’s the size of a date and this will give you some indication what flying is doing to your own moisture levels.”

When you’re flying at 38,000ft, humidity levels can be as low as 4 per cent, with research indicating the average body is stripped of up to 1.5 litres of water during a three-hour flight. To help counter the effects of looking (and feeling) like that shrivelled orange, Australian Medical Association vice president Tony Bartone says it’s essential to drink a little more than the standard eight glass of water a day, but also to avoid alcohol and caffeine where you can. “They’re deeply dehydrating, so stick to one glass or one cup and use eye drops to help relieve dry, tired eyes.”

WHY DO MY TEETH HURT?

As a rule, flight crew do not fly within 24 hours of having had dental work for the simple reason that changes in air pressure can often cause pockets of gas to get trapped within dental fittings or areas of dental decay, causing unimaginable pain. Short of reaching for painkillers, there’s little you can do once tooth pain begins aboard a flight so prevention is key. If you suspect a problem with your pearly whites, visit your dentist for a check-up well in advance of your flight and don’t schedule any dental work within a day of your departure.

WHY FOOD TASTES DIFFERENT IN THE AIR TO ON THE GROUND

While Michelin stars are likely to remain beyond reach of most (OK, all) airlines, the food served on-board is probably tastier than you think – or it would be, if you ate said dish with your feet firmly planted on terra firma.

The reason for the discrepancy is simple; when we’re flying, dry cabin air causes nasal mucus to evaporate and membranes to swell, so our perception of sweetness and saltiness can drop by as much as 30 per cent, according to a study by Lufthansa. Acceptance of your situation is at the heart of in-flight happiness, reveals Dr Bartone who warns against over-seasoning food to compensate. “By adding extra salt, you’re still hardly likely to taste it, but you do put yourself at more risk of dehydration.”

WHY DO I FEEL SO GROGGY?

As anyone who has bawled their way through a Sylvester Stallone movie mid-flight can attest, you are not entirely yourself up in the air – and there’s good reason you’re feeling so sleepy and/or emotional.

The air pressure in aircraft cabins is equivalent to what you would experience outside at 6000 to 8000ft, meaning your blood absorbs less oxygen (one UK study shows the average person’s oxygen level drops by approximately 4 per cent), causing sleepiness, headaches and a lack of mental sharpness.

While drinking plenty of water and avoiding alcohol and caffeine is recommended to help you combat these symptoms, there is nothing you can do about your new and concerning emotional fragility. But Dr Bartone does recommend sitting tall in your seat to allow oxygen to flow easily through your body, and to undertake regular breathing exercises. “Every 30 minutes or so, take in a series of deep breaths, hold briefly and exhale slowly,” he says. “Shallow breathing will only make you feel more sluggish.”

WHY DO I ALWAYS DISEMBARK WITH A COLD?

If you seem to punctuate each flight with the World’s Worst Cold, you’re far from alone; according to research compiled by Compare Travel Insurance, the likelihood of getting the sniffles is more than 100 times higher during a flight.

The data makes sense, says Steven Reed, who adds flight crew are given upper respiratory infection leave in addition to regular sick leave, such is the risk. “You could be sitting next to any number of people who are ill – even if they don’t quite yet know it – and the air that they’re breathing is recirculated and breathed in by you,” he says. “And even though that air goes through HEPA filters, how well they work really depends on how often they’re cleaned.” Frighteningly, a further study by Auburn University found disease-causing bacteria such as E.coli can survive for up to a week inside plane cabins.

Short of wearing a mask everywhere you go, the only way you can help battle the dreaded lurgy is by ensuring you arrive for your flight rested, relaxed and fighting fit, says Dr Bartone. “Bolster your immune system by eating plenty of fresh fruit and vegetables and drinking plenty of fluids in the week leading up to your flight,” he says. “And have plenty of sleep – getting on a plane in a stressed, exhausted state makes you a wonderful target for bugs and germs.”

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