A 1990 Massachusetts Institute of Technology study shows than an airline passenger stands a one-in-eight-million (1 in 8,000,000) chance of dying in a crash. That means you'd have to fly every day for 21,000 years before a plane you're in goes down.

General Aviation Accident Trends: General aviation accidents decreased by 3 percent from the 1,908 accidents reported in calendar year 1996. Chart 1 shows a downward trend in the number of aircraft accidents since 1978. Commuter and air taxi operations (covered by 14 CFR Part 135) were first excluded in 1975 from general aviation accident statistics. The overall accident rate decreased from 1996 to 1997, from 7.67 to 7.26 accidents per 100,000 hours flown. The number of persons killed increased to 640 (634 aircraft occupants) from the 632 who were killed in 1996. The fatal accident rate (1.38 fatal accidents per 100,000 hours flown) was lower than the 1.45 reported for 1996.

In-flight air quality has caused concern for pilots, flight attendants and passengers who fear that recirculated air may contribute to illness. Air is replaced 20 to 30 times an hour in modern jets. In a Boeing 767, this air circulating system works as follows: (1) Outside air enters the jet through its engine where it is compressed. Air then passes through cooling packs to a mixing chamber. (2) Outside air is combined with an equal quantity of filtered, recirculated air. The recirculated air has passed through high efficiency air filters similar to those used in hospitals and is essentially sterile. (3) Risers continuously take air from below the floor to the overhead cabin ventilation system. This overhead air distribution network runs the length of the cabin. (4) Air leaves the outlets and mixes with cabin air for two to three minutes. (5) Air is then exhausted through return air grilles. About half of the air will exit the plane, and the other half will be reprocessed to sterile conditions. (Source: Boeing / by Robert Davis, April Umminger and Bob Laird, USA TODAY. NOV 17, 2000)

Being packed like sardines on some flights, travelers are exposed to more illnesses, especially so during the cold and flu season. Influenza has been known to spread rapidly on airplanes, especially during long delays before take-offs when the air conditioning is turned down.

In 1979, a Centers for Disease Control and Prevention researcher found that 72% of passengers on a jet delayed for three hours on the ground in Homer, Alaska, caught the flu.

One contributory factor to more illnesses among fliers is "dirty cabin air." Unlike '60s-era aircraft, which continuously pull in fresh air from outside the cabin, newer planes offer a mix of new air and old air that is recirculated through on-board filters. The new "turbofan" jet engines depend on that air for fuel efficiency. The engines provide thrust by moving massive amounts of air with large fan blades. Drawing off air to circulate through the cabin makes the engines less efficient, burning more fuel and costing the airline more money.

One benefit to filtering and recirculating the air is increasing the humidity. The dryness of the air inside the cabin is a major health issue and drawing in more air from the outside would make it worse.

Another concern is that even the best airplane filters don't trap gases that could be harmful to humans, and may not stop all bacteria and viruses. With less outside air, "contaminant levels can rise quickly on the small and enclosed aircraft space.

Some minimize this concern saying that air inside the modern jet is exchanged between 20 and 30 times each hour, and the filters quickly pick up germs and other particles that float around the cabin. Some allege that filtered air is "crystal clear."

The following increases risk for in-flight illnesses: (1) Proximity to someone who is sick (2) The cumulative physical stress and strain of traveling (3) Low in-cabin humidity (4) Pressure: Once aloft, cabins are pressurized to roughly same levels found atop a 7,000 or 8,000-foot mountain. At 8,000 feet, oxygen is three-quarters what you have on the ground. For travelers with chronic breathing problems, lower pressure can have a medical impact.m (5) Vibrations and sounds: both of these shock waves may contribute to fatigue and may be a factor in disease transmission.

With longer international flights, concerns are raised about the transmission of more serious communicable diseases among travelers. A 1996 study published by the New England Journal of Medicine found evidence that tuberculosis can be transmitted between passengers and that the risk of transmission increased with duration of in-flight exposure. However, the study did note that the number of people flying with tuberculosis is probably very low, as little as one in 9 million, suggesting a very low risk of exposure to flight crews and passengers. (Gene Sloan and Robert Davis, USA TODAY: Nov 17, 2000)

(1) Stay home: unrealistic. (2) Wear a mask: drastic, awkward, too conspicuous. (3) Don't touch a thing: In such a confined space, there are layers of germs everywhere; so wash your hands as often as possible. (4) Stay moist: aircraft cabin air is incredibly dry ­ 10% to 20% humidity ­ making it easier for germs to spread. Use a saline spray to keep the nasal membranes moist. Drink plenty of fluids; a glass of water an hour. (5) Move: If the person next to you is sick, you don't stand a chance; if possible, move. (6) Relax: Stress is a huge factor. Minimize the preflight stressors as much as possible; pack ahead of time, get a good night's sleep. (7) Pre-boarding meal and drink (non-alcoholic): Eating and drinking increases the heart's blood output, sustaining the flow of oxygen to the brain and heart. Hunger is a risk factor for an in-flight emergency. People need to know it is easy to fall into hypoxia if they don't eat and drink before boarding a plane. (USA TODAY, Nov. 17, 2000)

Air travel decreases the partial pressure of oxygen in the blood and may cause symptoms in travelers with chronic lung disease. Pneumococcal and influenza vaccinations are appropriate. Supplemental oxygen is available on US airlines, but must be ordered in advance. Travelers are not permitted to use their own oxygen tanks in flight. In general, supplemental oxygen should be considered if the arterial PaO2 is likely to be 50 mm or less during flight. In-flight PaO2 may be estimated by measuring ground-level PaO2 and the FEV1 (as a percent of the predicted FEV1). The following formula was derived by Dillard and colleagues:  In flight PaO2 = 0.453*(Ground PaO2) + 0.386*(FEV1%) + 2.44. (Source: Emporiatrics: An Introduction to Travel Medicine by Mary D. Nettleman, M.D., M.S. Associate Professor, College of Medicine Director, Travel and Tropical Medicine Clinic University of Iowa College of Medicine, Iowa City, IA <http://www.vh.org/Providers/Textbooks/TravelMedicine/SpecMedPed.html#6>)

For some travelers, jet lag can be a terrible occurrence that may intrude into a major part of a short travel or vacation. Studies supports the use of melatonin for short-term treatment of jet lag. Caution must be exercised since melatonin is a recombinant human hormone, and the safety of long-term use has not been evaluated. A recommended jet lag protocol is: 0.3 mg synthetic melatonin tablets: (1) For eastward travel, take preflight melatonin in the late afternoon of departure and take post-flight melatonin for four days after arrival at local bedtime. (2) For westward flights, take melatonin at local bedtime for four days after arriving with a second smaller dose if there is early morning awakening. It should not be taken for more than one month at a time and not more than 0.5 mg per day, as long-term studies are not yet available. ·

Adverse effects: Sleepiness, impaired libido, mild depression at higher doses. Nausea, headache, nightmares. Possible decreased alertness and reproductive effects. Drug interactions with beta-blockers, CNS depressants, androgens and estrogens, SSRIs and MAOIs.

Caution: Do not use during pregnancy, lactation, in children, or if trying to conceive. Do not use if a patient has immune-system cancers. Do not use if a patient is on any drug that may interact with melatonin. (Source: Melatonin for Jet Lag by Joshua Ofman, MD & Jay Udani, MD)

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Links
The National Transportation Safety Board
Federal Aviation Administration

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