I've traveled more than 5 million miles by air -- far enough to get to the moon and back 10 times -- but I still get a sense of amazement when I'm in a fully laden 747 and we lift off. A million pounds of metal traveling at more than 200 mph, countering the force of gravity. It's a minor miracle.

Which is why it is so shocking when planes fall from the sky, as happened Monday with Air France Flight 447 from Rio de Janeiro to Paris, with a loss of 228 passengers and crew.

Reading about this, even a seasoned air traveler would be forgiven a twinge of anxiety. There is something unnatural about flight. Humans are nomads, evolving to walk across the savanna and forage for food and shelter. Driving is an accelerated mechanical version in which we still maintain indirect contact with the ground and see the landscape change in a familiar way. But to be in a sleek aluminum canister, six miles up and traveling at 80% of the speed of sound into blackness and near vacuum -- now that is unsettling.

All frequent fliers have stories to tell. I remember flying up the spine of the Andes one night from Santiago, Chile. There wasn't a cloud in the sky, but the 747 was tossed for an hour like a child's toy by clear-air turbulence. I imagined the flight crew up front, exchanging grim smiles as they wrestled with the controls.

Another time, on a night flight into Buenos Aires, we had to approach in a fierce electrical storm. The pilot announced that we might be diverted, but a while later, he said that we didn't have enough fuel to go to another airport. The message was clear: We had to land at Buenos Aires. This time it was the passengers who exchanged grim smiles.

Sometimes it's better not to know. Flying Pan Am a few years before it went out of business, I marveled at a landing at JFK, so smooth that the wheels started spinning and the shocks took the weight without anyone realizing we were down.

A little later, I found myself sitting next to the pilot in the waiting area. He was a tanned veteran, a silver fox, exuding experience and confidence. He talked about the principles of flight, and as I listened to his explanations, I realized he didn't understand Newton's laws or Bernoulli's principle. He didn't know how his plane flew!

And sometimes the incidents leave nothing to the imagination. Twenty years ago, my research advisor was on an Aloha Airlines jet for the short hop from Hilo to Honolulu. It was a flight I'd taken many times after working at the observatory on Mauna Kea. At 24,000 feet, the 737 suffered explosive decompression and the cabin started peeling open like a sardine can. The flight attendant who had just served my advisor a drink was sucked out of the plane and died. Two degrees of separation is too close for comfort.

But despite such incidents, air travel is fantastically safe. The death rate is about one fatality per 50 million passenger miles, making it 20 times safer than driving, according to a 2004 study by Harry Mantakos of Meretrix Technologies. You're more likely to die in your bathtub or by falling off a ladder than in an air crash.

The few times when planes fall from the sky -- the Japan Airlines flight in 1985 suffering a bulkhead rupture and crashing into the side of a mountain, two jets colliding in clouds over New Delhi in 1996, terrorism on Pan Am Flight 103 over Lockerbie, Scotland, in 1988 -- resonate because they are so final and so rare.

However, there is the possibility of failure any time human judgment and technology come into contact.

Once, when I was flying out of LAX on Lufthansa, the pilot announced a storm ahead and noted that we would "penetrate the thunderhead." In his clipped German tone there was confidence, and just a hint of hubris. Air France Flight 447 flew directly into an intense storm, passing through a "thunderous zone with strong turbulence," according to the air carrier. This would have subjected the airframe to lightning, hail and intense wind shear. It's possible that its fly-by-wire system was ill-suited to handle such dramatic changes in aerodynamic conditions or was incapacitated by lightning.

This terrible accident serves to remind us that our technology is impressive, but it's not invulnerable. A little more respect for the power of nature wouldn't be out of place.

Chris Impey is a professor of astronomy at the University of Arizona.