It is now thought that the mileage undertaken by air travellers worldwide is roughly the equivalent of 18,000 round trips to the sun each year so it is no wonder that health issues arise during these numerous journeys.
Aircraft crashes are very rare but the major loss of life understandably gets a lot of media publicity
Many travellers find air travel stressful. This does not simply apply to those with a fear of flying since struggling with the whole process can in itself be stressful, especially for the inexperienced and older, disabled and visually impaired.
Air travel involves much advance planning, the complexities of online booking, downloading boarding passes from the internet as well as organising all the required documentation
ensuring passports are valid, applying for visas, buying suitable tickets (usually now online), arranging foreign currency or informing the bank that so bank cards can be used abroad,
ensuring luggage is of the allowed size and weight, separating out liquids to pass through security and having details easily available if needed to complete disembarkation forms.
Money and the security of important items
It is essential that travellers inform their bank before going abroad so they can more quickly identify fraud occurring overseas. Some cards will not 'work' unless the bank knows where the traveller is.
At the airport there may be long queues passing through security, Removing items of clothing, being scanned and having hand baggage searched can all be stressful - more so if the staff themselves are very busy, also stressed or unhelpful.
Then there is the long and exhausting journey itself when aircraft noise, crowded cabins, inability to move freely around, the dry cabin air, limited toilet facilities, coping with eating from small plastic dishes in cramped conditions.
Humidity and dehydration
Cabin air is partly re-circulated and partly drawn in from outside the aircraft. It has dry air with a low humidity to protect aircraft equipment. This leads indirectly to increased loss of moisture through the respiratory tract and skin.
On long flights dehydration can develop if adequate fluid intake is not maintained and can be made worse by drinking alcohol.
Drying of the mucous membranes normally leads to thirst but the sensation of thirst is reduced as we get older.
Dehydration can increase the possibility of venous thrombosis.
Risk of infections
Recirculation of air is most unlikely to result in the spread of airborne infection as the re-circulated air is filtered removing particles much smaller than bacteria and viruses.
The air pressure in aircraft is kept to roughly the equivalent of 8000 feet above sea level which leads to discomfort and 'popping' of ears usually on the descent - especially distressing for infants who commonly cry because they do not understand what is happening.
This lower air pressure can cause difficulties for those with chronic respiratory problems and by arrangement oxygen may be arranged for those needing it through contacting the airline concerned well in advance.
Inability to equalise air pressure across the eardrum, sometimes due to a viral upper respiratory infection, can give rise to distressing ear pain on the ascent, but especially on the descent.
General advice about fitness to fly can be obtained from the traveller's doctor but airlines also have regulations, which can be obtained from the medical departments of the airlines concerned.
Infections which could be transferred to other passengers are usually stated as contraindications to air travel but, in practice, this does not include mild infections such as the common cold. Cases brought to the attention of the airlines' medical departments are decided on their individual merits
If travellers have chronic lung diseases such as chronic obstructive pulmonary disease (COPD) they may need to contact the airline in advance to request supplemental in-flight oxygen.
If there is a problem with bladder control it may be possible to arrange a seat near to a toilet. Cabin staff are usually very helpful.
Detailed guidelines on fitness to travel are available in the UK from the civil aviation authority
See also 'The older traveller' later in this course 2 and travelling when pregnant, with children and those with disabilities in course 7 .