IN SUMMARY: Ultra‑long‑haul flights increase exposure to immobility, low cabin pressure, low humidity, and fatigue. MedAire data shows serious events remain uncommon, but gastrointestinal symptoms and headaches rise with longer flights, highlighting the importance of prevention, trained crews, and real‑time medical support.
What changes as flights get longer?
As airlines push flight durations further,
up to 22 hours nonstop, crews and passengers spend longer in a confined environment with:
- Reduced cabin air pressure, equivalent to being at 5,000-8,000 feet
- Low cabin humidity, often below 20%
- Prolonged immobility
- Disruption of normal sleep-wake cycles
While most healthy travelers tolerate these conditions well, proactive planning, early risk identification, and effective in-flight medical support are important for maintaining safety and comfort on ultra-long-haul flights.
What health risks increase with flight duration?
BLOOD CLOTS (DVT/VTE)
Deep Vein Thrombosis (DVT) occurs when a blood clot forms in a deep vein, often after prolonged sitting. Although the overall risk is low, a 2007 WHO report identified evidence of DVT in longer flight durations:
- Relative VTE risk doubles after long-haul air travel >4 hours.
- Risk increases with travel duration and with multiple flights within a short period.
- Causes discussed in the report include prolonged immobility and venous stasis.
Who is at higher risk? Risk increases significantly when travellers have established VTE risk factors (e.g. prior VTE, malignancy, recent major surgery/trauma, pregnancy, thrombophilia, oral contraceptive use, obesity).
PRACTICAL STEPS
- ✓ Keep footwell space clear
- ✓ Perform simple ankle and leg exercises while seated
- ✓ Walk around the cabin when it is safe to do so
- ✓ Consider compression stockings if advised by a healthcare professional
- ✓ Seek medical advice before flying if risk factors are present
CABIN PRESSURE CHANGES
Aircraft cabins are pressurised to an altitude that slightly reduces the available oxygen. Most healthy passengers adjust normally however, passengers with pre-existing cardiopulmonary disease may be more likely to experience clinically meaningful symptoms.
PRACTICAL STEPS
- ✓ Use pressure-equalising techniques such as the Valsalva manoeuvre during ascent and descent
- ✓ For infants, feeding during take-off and landing can help equalise ear pressure
- ✓ Passengers with cardiopulmonary conditions should seek medical advice before travel
DRY CABIN ENVIRONMENT, DISRUPTED SLEEP AND ANXIETY
Extended time in a low-humidity cabin, crossing multiple time zones, and prolonged periods in a confined space can affect comfort, sleep quality, crew concentration, and overall wellbeing. While these effects are usually temporary and well-tolerated, they can contribute to fatigue, irritation, and heightened stress on longer flights.
PRACTICAL STEPS
- ✓ Use moisturiser, lip balm, or lubricating eye drops and consider wearing glasses instead of contact lenses
- ✓ Use eye shades, earplugs, or noise-cancelling headphones to improve rest
- ✓ Allow ample time for travel processes, practice simple breathing techniques, and moderate caffeine and alcohol intake
What the in-flight medical data shows (MedAire perspective)
MedAire's data shows that reported cases of DVT in-flight are relatively uncommon. However, the actual incidence may be higher, as many passengers may not recognise their symptoms or may attribute them to simple cramps, and therefore not report them to the crew. Some symptoms may also not occur until after the flight.
Looking at MedAire's 2024-5 cases the Gastrointestinal category saw the largest positive shift. At the symptom level, this meant higher rates of vomiting and headaches.
What it might mean: Longer exposure to dry cabin air, disrupted meals/sleep, motion sensitivity, and reduced hydration/food tolerance over time.
Your Medical Partner for Every Flight ProfileWhatever the flight length, MedAire delivers medical and security expertise tailored to your operations, combined with data‑driven insight into your routes, passengers, and risk profile. supporting crews to manage in‑flight risk and enabling safer, faster decisions from departure to destination.