Some guidelines on assessing fitness to fly are given below. However, different airlines have their own rules which can be checked with their medical adviser. A form (MEDIF) from the airline or travel agent should be completed by passenger and GP for any passenger with a relevant medical condition.

In general those with stable cardiac or respiratory conditions who can climb 12 stairs and walk 50 metres on the level without severe breathlessness or developing angina are fit to fly on commercial aeroplanes.

Those usually considered unsuitable for flying include those:

•   markedly dyspnoeic at rest;

•   with poorly controlled heart failure;

•   with uncontrolled arrhythmias;

•   with unstable angina;

•   with a haemoglobin below 7.5 g/dl;

•   with an infectious disease transmissible to other passengers;

•   patients with a psychotic illness, unless stable and escorted.

Poorly controlled epileptics may need an increase in medication. Pregnant women should not travel after 36 weeks, and a letter stating their expected date of delivery and that they are fit to fly is desirable from 28 weeks.

Flying will usually need to be delayed for at least ten days after chest or abdominal surgery (even keyhole), and after a GI bleed, an uncomplicated myocardial infarction or a cerebrovascular accident with good recovery. It is advisable to wait 24 hours after a plaster cast is applied before a flight of under two hours and 48 hours if the flight is longer (or bivalve the plaster). Neonates should be at least 48 hours, and preferably at least two weeks, old before flying.

Facilities which may be available for pre booking for air travel

Equipment such as wheelchairs or other transport will be available within the airport and preboarding may be possible. On the plane a seat near the lavatory, an extra seat if necessary for a plaster cast (though the seat will have to be paid for), special dietary requirements and supplementary oxygen can be requested.

All travellers with pre-existing medical conditions are advised to declare their diagnosis to the insurance company and to carry their medication in their hand luggage with a separate note of its generic name and the dose.

13.2  Deep vein thrombosis

Any travel involving prolonged immobilisation, by land or air, can result in a deep vein thrombosis (DVT) with the risk of pulmonary embolus (PE). Those at increased risk include people with a history of thromboembolic disease, women taking an oral contraceptive or who are pregnant, those recently hospitalised, especially following major surgery, the obese, some patients with congestive heart failure, people with paralysis of the lower limbs and people with malignant disease. Dehydration may increase the risk.

Periodic flexion and extension exercises of the lower limbs, deep breathing exercises and walking around where feasible, are advised to help reduce the risk. People on long haul flights should also be advised to drink plenty of water and avoid excess coffee or alcohol. Those who are considered to be particularly at risk of DVT or PE need expert medical advice for the journey. Elastic support stockings, low dose aspirin, or anticoagulants (warfarin or low molecular weight heparin) may be prescribed.

13.3  Cruises

Those with pre-existing medical conditions may be considered more suitable for cruising than flying. This may exclude cruises involving a flight to join the ship. Medical facilities on board vary and travellers should be advised to enquire before they book. They should also realise that occasionally those with an acute medical emergency may have to disembark at whatever port is nearest whilst repatriation is arranged.

Rough weather may induce sea sickness. Although motion sickness is less likely on a larger ship, in some itineraries transfers may be necessary from the cruise ship to smaller vessels in order to go ashore. These may also require more agility and injuries have occurred.

Whilst eating and drinking on board is often considered safer than onshore, outbreaks of gastrointestinal infections or respiratory tract infections including influenza have occasionally occurred on board.

13.4  Jet lag

Long distance travel by land, sea or air can expose the traveller to tiring, crowded and stressful conditions with variable availability and suitability of meals and opport-unities to sleep. When air travel crosses many time zones, additional symptoms on arrival can be caused by a lack of physiological adaptation to the local time.

Individuals are affected to varying degrees, increasing with the number of time zones crossed and tending to increase with advancing age. Adaptation to eastward travel generally takes longer than westwards.

Many proposed 'jet lag' regimens have little proof of efficacy but travellers can be advised to sleep/nap on flights to reduce the sleep debt and keep hydrated with plenty of water. A flight which arrives shortly before the local bedtime can be helpful. A few days acclimatisation to the new time zone should be allowed where performance of skilled tasks is important.

Research is being conducted into the careful timing of exposure to bright light, timing of meals and caffeine intake, exercise, sleep and naps. Research into the use of melatonin is also being undertaken. Melatonin is a pineal hormone which aids the circadian rhythm to shift to sleep/night mode. There are no long term toxicity studies. It is unlicensed in the UK and not reccommended for routine use at present.