Most healthy travellers do not experience any problems during long flights.
However, the risk is higher for people who have recently undergone surgery, are pregnant, are living with obesity, have a family history of blood clots, or use estrogen-based contraception, according to the NHS, as cited by Express.
Simple advice during the flight
The NHS recommends that passengers get up and walk around the cabin whenever possible.
It is also a good idea to drink plenty of water, wear loose-fitting clothing, and move your legs, feet, and toes regularly.
Also read: Study links unhealthy fat cells to higher diabetes risk
Dr. Syed Nadeem Abbas of Knee Pain Clinic UK also advises against sitting with your legs crossed.
Instead, travellers can make small ankle movements and raise their heels to help keep their blood circulating.
For some people at higher risk, compression stockings may also be beneficial.
The NHS also advises against drinking excessive amounts of alcohol before and during a flight, as it can lead to dehydration and reduce physical movement.
Also read: Trying to lose weight? Your calorie deficit could be too large
Why movement matters
The reason for these recommendations is the risk of deep vein thrombosis (DVT).
According to the NHS, the risk may increase on journeys lasting four hours or longer because blood circulates more slowly when you remain seated for extended periods.
DVT usually develops in the leg and can cause swelling, pain, warmth, or redness. However, some people experience no symptoms.
In rare cases, the blood clot can travel to the lungs and develop into a pulmonary embolism, which requires emergency medical treatment.
Also read: How cabbage can affect your body if you eat it regularly
For this reason, both the NHS and Dr. Syed Nadeem Abbas recommend moving around regularly during long flights.
Also read: Could humans live to 200? Scientists have a new answer