Airplane pilots call it clear-air turbulence. You're flying along -- everything should be even. For no apparent reason, you hit waves.

That describes last week's action in the financial markets. To give just one example, the Dow Jones Industrial Average dropped 538 points to its lowest level since Oct. 27, and is now 11% below its Jan. 14 high.

The week began with clear skies. Everything seemed completely under control on Monday and Tuesday. The active long-bond futures were at a two-month high. Nasdaq 100 futures rose 4.8% in two days. Gold fell below $300 an ounce. The ice was melting, and the air was balmy. Visibility, as pilots say, was unlimited.

Then, as happens so often in the market, the wolves jumped out of the bushes. As in nature, when the prey is lulled into a sense of calmness, the predators are most dangerous, because an attack is less expected.

When S&P 500 futures reached 1450 on Tuesday, that was the turning point. On Wednesday, they came close, but couldn't top the high. By Friday, the market hit turbulence. That afternoon was as scary for traders' financial lives as the week's hijack of an Afghan Airlines jet was for passengers.

At the worst part, when the U.S. indices fell to the day's lows, the Chicago Board Options Exchange's volatility index, or VIX, came within a point of 30.

A reading of 30 on the VIX over the past two years has been perhaps the best tell of all of a substantial market rally. The index is based on the price of options and reflects expectations for volatility. The VIX most recently touched 30 on Jan. 5 and Jan. 25, and that was good for a 5% market rally in the next four days in each case.

Reviewing the market from the comfort of the armchair, it was a typical week. The Nasdaq was up a few percent; the S&P 500 was down a couple percent; the Dow was down substantially; and gold and bonds were basically unchanged. After the tremendous gains of last week, it was normal for the market to react.

But amid the balmy breezes, we have some doubts. England, for one: The FTSE 100 is now down 12% on the year. Complacency is another: The S&P 500 futures have now opened up seven times in a row, responding to overseas euphoria as stock indices in Germany and Hong Kong set all-time highs and the Nikkei topped 20,000 for the first time since July 1997.

And that miraculous recovery in the market in the final 20 minutes of trading on Friday may have lulled people. S&P 500 futures, which at one point were within a point of the 35-point limit down, came back 11 points. The Dow average regained about 70 points.

Unlike great pieces of 19th century classical music, the market doesn't give us heroic endings to give us peace of mind so we can go home and have a pleasant evening with our beloved. A much more likely reason is to keep us coming back for more, so our chips will be in place for a killing blow in the future.