What Flying Does to Your Body (and How Crew Fight Back)

The cabin is a mild altitude environment — your body notices

A pressurized cabin at cruise sits at the equivalent of 6,000–8,000 feet of altitude (newer aircraft like the A350 and 787 hold closer to 6,000). Your blood oxygen saturation drops a few percentage points, gases in your body expand by up to 25–30%, and relative humidity falls to 10–20% — drier than most deserts. None of this is dangerous for healthy crew, but doing it 80+ hours a month means the small effects add up, and the crew who feel best at year ten are the ones who ran countermeasures from year one.

Skin, eyes and the 10% humidity problem

At 10–20% humidity your skin loses moisture to the air continuously, your tear film evaporates faster, and mucous membranes in your nose and throat dry out — which is also why minor nosebleeds and scratchy throats are common on long sectors. The fix is barrier-first, not just hydration: drinking water helps overall, but skin needs occlusive protection to stop the loss.

• Apply a heavier moisturizer than you'd use on the ground before every flight — look for ceramides or squalane, and reapply on ultra-long-haul
• Lip balm and hand cream live in your uniform pocket, not your bag
• Contact lens wearers: carry preservative-free lubricating drops, or switch to glasses on night sectors — dry eyes plus recirculated air is the classic red-eye combination
• SPF matters at altitude: UV exposure through cabin and flight deck windows is real on daytime sectors, and crew show elevated rates of skin damage — a daily SPF 30+ is the cheapest insurance in aviation
• A saline nasal spray before and during flight keeps nasal passages moist — drier membranes are also worse at filtering germs

Cosmic radiation: the honest numbers

At cruise altitude the atmosphere shields you less, so crew receive more cosmic radiation than almost any ground profession — typically 2–5 millisieverts per year for a full long-haul roster, compared to roughly 2–3 mSv of natural background exposure everyone gets at sea level. EU rules require airlines to assess exposure and keep crew below 20 mSv/year (a threshold working crew essentially never approach), and to adjust rosters for pregnant crew so the fetus stays below 1 mSv.

Perspective matters here: a busy flying year roughly doubles your natural background dose. That is a real occupational exposure worth knowing about — polar routes and high-latitude flying carry more, and airlines operating them track it — but it is far below the levels associated with clear harm. The sensible responses are the ones regulators already mandate: exposure tracking at EU carriers (you can request your figures), and telling your airline as early as possible if you're pregnant so your roster is adjusted.

Bloating, digestion and circulation

Gas expansion at cabin altitude is why you bloat on board even eating nothing — the air already in your gut expands by a quarter to a third. Combine that with irregular meal times and sitting through crew rest, and digestion is one of crew members' most common complaints. Circulation is the other: hours of standing plus low cabin pressure means fluid pools in your lower legs, and crew have a genuinely elevated occupational reason to care about vein health.

• Compression socks (15–20 mmHg, or 20–30 for long-haul) on every flight over 4 hours — the most universally endorsed item in crew culture, for good reason
• Skip the classic bloat triggers before and during flights: carbonated drinks, large portions of beans/cruciferous vegetables, chewing gum (swallowed air), and very salty crew meals that drive water retention
• Eat smaller portions more often on duty rather than one large meal — your gut handles it better at altitude
• Calf raises and ankle circles during quiet phases; walk the cabin length when service allows — movement is the pump your veins rely on
• On layovers, prioritize fiber and fermented foods to reset — the roster-life gut does badly on airport food alone

Hydration and your immune system

The working number most airlines teach: drink roughly 250 ml (a cup) of water per hour of flight, more on ultra-long-haul, and treat coffee and alcohol as partially subtracting from that total. Chronic mild dehydration is behind a surprising share of crew headaches, fatigue and dry-skin complaints — a collapsible bottle you actually refill beats any supplement.

On immunity: you're exposed to hundreds of people in a confined space while jet lag suppresses your immune response — the reason new crew famously get sick constantly in year one. HEPA filtration on modern aircraft is genuinely excellent (cabin air is fully exchanged every 2–3 minutes), so the bigger risks are surfaces and your own run-down state. Hand hygiene before eating, not touching your face during service, the flu jab each season, and — above all — protecting sleep are what veteran crew actually credit for staying healthy. Most also report their immune system 'catches up' after the first year or two.