Flying puts the body under physiological stress, causing bloating, fatigue, and dehydration. While not dangerous for healthy travellers, the body adjusts quickly. At 35,000 feet, altitude, dry air, and gas expansion explain why passengers often feel unwell upon landing. Experts from the UK share insights on what happens and how to reduce the impact.
Pre-flight stress and psychogeography
Pharmacist Thorrun Govind explains that stress hormones often rise before boarding due to crowds, queues, and the unique environment of airports. Psychogeographers view airports as liminal zones where boundaries fade, creating disorientation. Steve Taylor, Senior Lecturer in Psychology at Leeds Beckett University, notes that losing control over time can cause anxiety, raising stress levels long before takeoff.
Physiological changes at altitude
After takeoff, cabin pressurisation simulates an altitude of 6,000 to 8,000 feet. Blood oxygen levels drop from about 97% to 90%. This is not harmful for healthy people but can cause brain fog and fatigue due to reduced oxygen to the brain. Cabin humidity is only 10-20%, compared to 40-50% at home, causing moisture to evaporate from the skin, eyes, nose, and throat. However, Thorrun clarifies that this does not cause whole-body dehydration; it primarily affects external surfaces. Contact lens wearers often notice dryness first.
Alcohol exacerbates fluid loss, leading to thirst and headaches. Cabin pressure also dulls taste by suppressing sweet and salty flavours while enhancing savoury ones, explaining why tomato juice and Bloody Marys are popular in-flight. Background noise from engines may also affect taste perception.
Gas expansion and ear popping
According to Boyle's Law, as cabin pressure falls, trapped gas in the body expands, causing bloating. Similarly, trapped air in the middle ear and sinuses must adjust, resulting in the sensation of ears popping. These effects are temporary and resolve after landing.
Tips for frequent flyers
Thorrun Govind advises moving regularly on flights to maintain circulation, staying hydrated, limiting alcohol and caffeine, and protecting sleep when crossing time zones. Compression socks and exposure to daylight after landing can also help. Wellness expert John La Puma recommends assuming the time zone of your destination immediately. He says, 'The next day get outside for daylight first, before coffee or your phone. Short intentional time outdoors resets your body’s clock more than anything indoors.' He adds that under three time zones, the body adjusts on its own within a day or two, and the issue is often being indoors at the wrong time rather than jet lag.
