“My wife and I decided not to fly anymore,” a friend said to me last weekend. “The damn machines have forgotten how to fly, or their pilots have. They keep falling out of the sky.”

Not true. Airplanes are made to fly. They stay in the air because it’s their nature, just as it’s the nature of boats to float. When a plane goes down – as an Indonesian airliner did on Sunday, with 49 passengers and a crew of five, which prompted my friend’s outburst – it’s for reasons that, though often complex, are rarely mysterious.

Flying machines can come to grief in innumerable ways, but here are 10 favourites.

1. A plane can be deliberately shot down. You’d think this is unusual in peacetime, but it’s not as unusual as you’d think. Since the 1970s, its happened to two Korean Air 747’s, an Iranian Airbus, a Sri Lankan Antonov, three Georgian Tu-154s and one Tu-134, plus two Rhodesian passenger planes and a Siberia Airlines Tu-154, among others. Most recently it happened to Malaysia Flight 17 over Ukraine.

2.  A plane can be bombed, hijacked or otherwise sabotaged. This isn’t unusual either, owing to terrorists born and bred in every part of the world, though in some parts and periods more often than in others, such as the Middle East in our day. Shooting down or blowing up airplanes has to do with political dynamics, of course, not aerodynamics.

3.  A plane can have a midair or ground collision with another object – civilian or military. Sometimes even a natural object – i.e., a bird. Collisions aren’t frequent – it’s a big sky – but no month passes without one. Aviation’s worst loss of life came in 1977 from a ground collision of two wide-body passenger jets over Tenerife, Canary Islands.

4.  An aircraft can fly into the ground (or an obstacle sticking up from it) resulting in a notorious type of accident called a controlled flight into terrain (CFIT). CFITs are usually caused by human error, sometimes combined with equipment failure or malfunction, resulting in a loss of what aviators call “situational awareness.” In simple language, it means a pilot flying a perfectly good machine into a hill because he doesn’t know where the hell he is. It usually happens at night or in poor visibility, though it can happen in visual meteorological conditions if a crew becomes distracted. Notorious CFITs included a tragic crash of a U.S. airliner in Cali, Colombia, as well as the loss of U.S. Commerce Secretary Ronald H. Brown’s flight in the former Yugoslavia.

Flying is dangerous. Oh well – so is living.

5.  A plane can suffer a catastrophic failure of a vital structure, such as a wing or a fuselage component. This is very rare, but it can happen as a result of metal fatigue caused by age, defective manufacturing, or improper maintenance. Three examples have been a Turkish DC-10 near Paris in 1974, killing 346; an American DC-10 near Chicago in 1979, killing 275; and a Japan Air Lines 747 in 1985, death toll 520, the worst single-plane air disaster ever. A similar danger is uncontained failure of an engine that destroys flying surfaces or flight controls, as happened to a United DC-10 at Sioux City, Iowa, in 1989.

6.  An aircraft can encounter an unlucky sequence of adverse events, minor in themselves – ranging from failure of some non-vital component to inclement weather and traffic delays – that in combination overwhelm the crew. A plane may suddenly lose pressurization, as may have happened to golfer Payne Stewart’s Learjet in 1999, giving no time for the pilots to go on supplementary oxygen. A few years ago, a South American airliner crashed near New York because a series of delays at JFK airport, coupled with communication problems, resulted in fuel exhaustion. Another South American airliner was lost when ground workers left some masking tape on the fuselage after washing it, resulting in erroneous instrument readings that confused the pilots.

7.  A component in a highly complex machine can start acting in ways unforeseen by engineers and pilots. Unusual as this is, it does happen sometimes with catastrophic results. It’s on such occasions that the cockpit voice recorder recovered from the wreckage contains lines like, “What’s it doing now?” as some equipment on the flight deck seems to acquire a mind of its own. The 1994 crash of a USAir Boeing 737-300 near Pittsburgh may fall into this category; it could have been caused by the uncommanded deployment of the plane’s rudder. The spontaneous deployment of a thrust reverser in flight may have caused the crash of an Austrian Lauda-Air Boeing 767-300 over the Thai jungle. A midair collision was narrowly averted some years ago near Albany, N.Y., when a collision avoidance system commanded one plane to climb into another.

8.  In-flight fire from a variety of sources can create a nightmarish emergency. Whether it’s dangerous cargo, as in the ill-fated Valuejet flight over Florida, or an electrical short in the on-board entertainment system, as suspected in the Swissair tragedy off Nova Scotia, smoke or noxious fumes can incapacitate a crew in a short span of time. In 1980, 301 people perished when a Muslim pilgrim’s butane stove set a Saudi Arabian Lockheed 1011 Tristar ablaze after taking off from Riyadh.

9.  The latest generation of computerized “glass cockpits” may let pilots fall though a crack between their traditional role as hands-on aviators and new role as systems managers. Flying skills may deteriorate because of insufficient use; attention may flag because of high automation, until a situation develops where, between man and machine, nobody’s minding the store. The loss of an Air France Airbus on a flight from Rio de Janeiro to Paris a few years ago has been attributed to the crew’s inability to hand-fly the plane after icing caused the autopilot to quit.

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These nine causes together probably account for about 70 per cent of all airline mishaps. The other 30 per cent are caused by No. 10: assorted lapses of judgment. Pilots, engineers, mechanics and air traffic controllers do stupid things at times. So do other people, but flying is less forgiving of mistakes. Preliminary reports seem to point to human error as the cause of Sunday’s crash.

Hmm. Reading what I’ve just written, I may have inadvertently proved my friend’s point. Flying is dangerous. Oh well – so is living.

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