Twenty-Five Things You Didn't Know About Flying
Almost everything odd about a commercial flight is odd for a reason, and the reason is usually either physiology, safety engineering or a regulation written after something went wrong. Twenty-five oddities, each with the explanation.
12 min read
Flying is the most heavily engineered routine experience most people have. Every detail in the cabin — the lighting, the meal, the safety card, the hole in the window — has been decided by someone with a specific problem to solve. Here is what they were solving.
Your senses, at 11,000 metres
| # | The oddity | The reason |
|---|---|---|
| 1 | Airline food tastes bland | Not the catering's fault. At cruise, cabin pressure is equivalent to roughly 1,800–2,400 m of altitude and humidity drops to around 10–20% — drier than most deserts. That combination dulls the perception of sweet and salty tastes by something in the region of 20–30%, and dries the nasal passages, which removes much of what we call flavour. The constant background noise at around 85 dB measurably reduces sweetness perception further. |
| 2 | Everyone orders tomato juice | The direct consequence of #1. Umami and sour tastes are far less affected by altitude and low humidity than sweet and salty. Tomato juice is rich in umami, so it tastes roughly the same aloft as on the ground — while wine, dessert and almost everything else tastes worse. A German airline once measured tomato juice consumption on board at a level that vastly outstripped its popularity on the ground. |
| 3 | Airlines over-salt and over-season deliberately | Catering is developed to be tasted in a pressurised chamber or with the known reduction factored in. Food that tastes correct on the ground will taste flat in the air, so recipes are built with more salt, more acid and more umami than a ground kitchen would use. |
| 4 | You feel bloated | Gas in your intestines expands by roughly 25–30% at cabin pressure, following the same physics as the crisp packet that inflates in the overhead bin. It is entirely normal and entirely unavoidable. |
| 5 | Alcohol seems to hit harder | The evidence is mixed on whether it actually does — blood alcohol behaves similarly at cabin altitude. What is well established is that mild hypoxia and dehydration produce symptoms that resemble intoxication, and that recent sleep research has found alcohol plus cabin altitude puts measurably more strain on the cardiovascular system during sleep than either alone. |
Things in the cabin that look like mistakes
| # | The oddity | The reason |
|---|---|---|
| 6 | There is a tiny hole in your window | Aircraft windows are three panes. The outer pane carries the pressure load. The small hole — the bleed hole — is in the middle pane, and it lets cabin pressure reach the gap so that the outer pane bears the differential alone, as designed. It also lets moisture escape, which is why your window is not permanently fogged. It is the most reassuring hole in aviation. |
| 7 | Lavatories still have ashtrays, decades after smoking was banned | Because the certification requirement was never removed, and for a good reason: the rule assumes someone will break the smoking ban, and a designated non-flammable receptacle is safer than a paper towel bin. The 'no smoking' placard and the ashtray beneath it are both required. |
| 8 | The lavatory can be unlocked from outside | Under the 'Occupied' sign there is a hinged flap covering an external latch. Crew need to be able to open the door in a medical emergency. It is on every commercial aircraft. |
| 9 | There is no seat letter I | A capital I is too easily misread as a 1 or a lowercase l. Seat letters run …G, H, J, K. Many airlines also skip row 13, some skip row 17 (unlucky in Italy), and airlines with large East Asian markets frequently skip row 4, because the word for four is a near-homophone for death in several regional languages. |
| 10 | Some seats have a small triangle above the window | It marks the row with the best view of the wing, and it is there for the crew, not you — it identifies the seat from which the slats and flaps can be inspected visually. It also tends to be the quietest window seat, since it is forward of the engine exhaust line. |
| 11 | The 'black box' is bright orange | So it can be found. It has a heat-resistant, high-visibility casing and an underwater locator beacon. The name is a piece of British engineering slang that stuck. Modern aircraft carry two — a flight data recorder and a cockpit voice recorder — designed to survive around 3,400 g of impact and an hour at 1,100 °C. |
Procedures that make sense once explained
| # | The oddity | The reason |
|---|---|---|
| 12 | The cabin lights are dimmed for takeoff and landing | Dark adaptation. If an evacuation becomes necessary in darkness, eyes already adjusted to low light can see the aisle and the exits. Fully light-adapted eyes take tens of seconds to adjust — time that does not exist in an evacuation. The same logic requires window blinds up: so crew and passengers can see outside conditions, and so external light can enter. |
| 13 | Takeoff and landing are when everything gets strict | Because that is when almost everything happens. Roughly two-thirds of accidents occur during takeoff, initial climb, approach and landing — a period that accounts for a small fraction of flight time. This is the origin of the pilots' rule of thumb about 'the critical eleven minutes': the first three after takeoff and the last eight before landing. |
| 14 | Cabin crew stand with their hands behind their backs during boarding | Frequently they are holding a counter, tracking passengers boarding. The posture is also a trained neutral stance. Separately, crew sitting on jumpseats during takeoff and landing are performing a 'silent review' — mentally rehearsing their specific exit, commands and drills for that phase. |
| 15 | The captain and first officer eat different meals | Deliberate policy at many airlines: if one meal causes food poisoning, it should not incapacitate both pilots. Some carriers additionally source the two meals from different batches. |
| 16 | The brace position looks uncomfortable rather than protective | It is designed to reduce flailing injury and secondary head impact by pre-positioning the body against the seat in front, so that deceleration forces are absorbed in a controlled way. It is the product of decades of crash-survivability research, not a comfort compromise. |
| 17 | You are told to put your own oxygen mask on before helping others | Time of useful consciousness at cruise altitude after a rapid depressurisation is on the order of 15–30 seconds. An adult who helps a child first may not be conscious to help anyone. It is the most literal 'put your own mask on first' in existence. |
The aircraft itself
| # | The oddity | The reason |
|---|---|---|
| 18 | Aircraft are struck by lightning about once a year each, and nobody notices | The airframe acts as a Faraday cage: current travels over the aluminium or through embedded conductive mesh in composite structures and exits via static discharge wicks on the trailing edges. Certification requires it. Damage is usually a small burn mark found in inspection. The last confirmed loss of a commercial airliner primarily to lightning was in 1967, and the fuel-tank protections introduced afterward are why. |
| 19 | Planes are almost always white | Four reasons, all practical: white reflects sunlight and keeps the cabin and fuel cooler, it does not fade, it makes cracks, dents, corrosion and fluid leaks visible during walkaround inspections, and it is lighter — a full custom livery on a wide-body can add several hundred kilograms of paint, which is fuel burned for the life of the aircraft. |
| 20 | The cabin air is cleaner than most offices | Air is fully exchanged roughly every two to three minutes, mixing outside air compressed by the engines with recirculated air passed through HEPA filters that capture upwards of 99.9% of particles at the relevant sizes. Airflow is designed to move from ceiling to floor, laterally rather than along the cabin. The dryness is the trade-off: outside air at altitude contains almost no moisture. |
| 21 | Tyres are inflated to around 200 psi and do not burst on landing | Roughly six times a car tyre. They are filled with nitrogen rather than air, because nitrogen is inert, does not support combustion and changes pressure less with the extreme temperature swings of a landing. A main tyre is typically rated for hundreds of landings before retreading, and touching down at 250 km/h spins it from zero to full speed in under a second — which is what the puff of smoke is. |
| 22 | A twin-engine airliner flies perfectly well on one engine | Certification requires it, including a takeoff continued after an engine failure at the worst possible moment. ETOPS approvals then govern how far from an airport a twin may operate — up to 330 minutes on one engine for some types, which is what makes ultra-long-haul over the Pacific and the Arctic legal. |
| 23 | The doors cannot be opened in flight, at all | Not a matter of strength or willpower. Cabin doors are plug-type: pressure differential at cruise presses them into the frame with a force measured in tonnes. Even a determined person cannot overcome it, and the mechanism is designed so the door must move inward before it can move out. |
| 24 | Most aircraft can land themselves, and almost never do | Autoland has existed since the 1960s and is certified for the lowest-visibility categories, where a manual landing is not permitted. In normal conditions crews land manually — because hand-flying skill degrades without practice, and because autoland requires specific ground equipment, specific aircraft status and a longer, more constrained procedure. The automation is for when conditions are bad, not for when they are good. |
| 25 | A Boeing 747 is made of roughly six million parts | About half of which are fasteners. The aircraft contains something on the order of 240 km of wiring, and the wing area is large enough to park several dozen cars. The last passenger 747 was delivered in 2023, ending 54 years of production — the type is now mostly a freighter, and the aircraft that ended it is the twin-engine wide-body that does the same job on half the engines. |
Two bonus curiosities about the language
“Mayday” comes from the French m’aider — help me — chosen in the 1920s by a radio officer at Croydon Airport because it was unambiguous over poor radio to both English and French ears. It is said three times to prevent it being mistaken for part of a sentence. “Pan-pan”, from panne (breakdown), is the tier below: urgent, but not immediate danger to life.
And “Roger” means only “received” — it was the letter R in the pre-NATO phonetic alphabet, and R stood for Received. It does not mean agreement or compliance; that is “Wilco”, short for “will comply.” Which is why saying “Roger Wilco” is slightly redundant, and why nobody in aviation says it.
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