The Federal Aviation Administration has decreed that all aircraft certified since 1988 must install superstrong airline seats that won't break apart during a "survivable" crash. So at a cost of $5 billion over 10 years, all U.S. airlines are voluntarily retro-fitting their seats.

But this has generated a new problem. Many passengers face an additional danger: if the seat in front acts as a buffer, one's head suddenly becomes a 260-pound bowling ball on impact -- swinging it down to one's knees or even the floor.

So the airlines are having to spend another $600 million -- on top of a developmental cost of $25 million -- for airbags to cushion a crash shock when the new seats are installed.

Is the money, and the increase in fares it will prompt, justified?

• Of the 364 U.S. airline accidents between 1983 and 1996, 24 were deemed very serious by authorities and 17 were called "survivable."

• Of the 1,759 passengers on those 17 survivable flights, 78 percent survived, 15 percent died from blunt-trauma injuries, and five percent died from smoke inhalation or fire.

• Airbags or some other extra restraint may have helped save the 15 percent -- and some of the 5 percent may have gotten out if they hadn't been knocked out by the impact.

• So experts believe that the new airbags will save no more than 25 lives a year -- at a total cost of $5.6 billion.

Out of 700 million passengers who fly each year, only 160 persons lose their lives, on average.

Source: Howard Banks, "In for a Dime, in for $5.6 Billion," Forbes, October 4, 1999.