A review in The Lancet by researchers from the US suggests that authorities need to be aware of the risks of health problems such as blood clots and the potential for flu pandemics as an ageing population take to the skies.
A review of a number of studies suggests that extended flight times has raised the risk of venous thromboembolism. About 75% of these cases have been linked to lack of movement while on boar a flight, with economy class passengers more likely to develop this condition than those in business class.
The risks start to rise at four hours and are highest at eight hours. The new larger aircraft such as the Airbus A380 and the Boeing 777-LR could potentially extend flight times to 20 hours, although there would be better facilities aboard these aircraft, which might lessen the risks.
Spending long periods in a highly pressurised environment also carries risks, according to the review. People with existing respiratory problems may experience a worsening of their condition and people who have had recent surgery may suffer as a result of expansion of gases in the body.
According to the authors, people should be able to walk at least 50 metres and climb a flight of stairs without becoming short of breath in order to be deemed fit to travel. However, this risk is generally restricted to within two rows of passengers carrying the infection.
The UK Civil Aviation Authority last year issued a set of guidelines for health professionals to help them decide who is fit to fly.
Long periods of close exposure is also known to spread disease and outbreaks of flu, severe acute respiratory syndrome (SARS) and tuberculosis have been associated with air travel in the past.
