They catch your eye while you are sitting at an airport waiting for your flight -- those big black machines that sell flight insurance, the ones with the nervous-looking travelers hovering over them carefully reading instructions.

Since Mutual of Omaha introduced them to airports in 1955, the insurance machines -- for a modest sum -- have assured passengers that loved ones will be well taken care of should a round-trip flight unexpectedly turn out to be one-way.

Mutual of Omaha has insured flyers for their encounters with the wide blue yonder for 30 years, peddling policies out of big, black, 3 1/2-foot-high boxes bearing the company's Indian logo. Now considered a supplement to insurance sold over the counter, they offer two types of flight insurance -- commercial and chartered.

The policy insures the buyer only for the flight, but for as little as 50 cents. The maximum $5 policy on a commercial flight provides insurance worth $150,000, while the maximum coverage on a chartered flight is $50,000 for a $2 fee.

Even though the boxes are convenient to passengers who decide to get coverage at the last minute, most people opt for the more complete coverage available over-the-counter at booths set up around the airport or from a travel agent.

Mutual of Omaha has approximately 200 machines stationed at 130 airports throughout the United States and some in Canada. They constitute a tiny percentage of the 1 percent that the travel insurance business contributes to Mutual of Omaha's $2.1 billion business.

"They are more of an advertisement for the company than a profit margin," said Tom O'Connor, a spokesman for Mutual of Omaha in Nebraska.

A quick reading of the machine policy indicates that it provides very limited coverage. In fact, the coverage is quite specific and reads a little like a Stephen King horror story:

"Loss of life yields the principal sum; or loss of both feet or both hands or both eyes; loss of one hand and one foot; or loss of one hand and one eye or one foot and one eye, all are paid with the principal sum."

"I know it sounds gruesome, but we have categorized each loss and the payment for that loss just as we would a normal insurance policy," O'Connor said.

Stephen Eidsness, a supervisor at the Continental Airlines counter, maintains the machines at Dulles International Airport. He keeps them stocked with policies and makes sure they are working.

"There are a lot of people milling around who happen upon the machines and see that you can get insurance for coins," he said. "They are intimidated by an insurance booth."

If there is ever an accident involving a plane that departed from the airport, Eidsness must quickly shut down the machines to prevent someone from filing a fraudulent claim in the name of a passenger. He said there has never been an airplane accident while he has had custody of the machines.

The two machines at Dulles were replaced only once, because their color "clashed" with the colors prescribed by the restrictive codes at the airport.

Because the machines are no longer made, they had to be replaced with gray machines left over from the 1950s. Eidsness recently asked Mutual of Omaha for an additional machine for the new South Concourse.

"It's easier for people to 'talk to a machine,' " observes Eidsness. "A lot of people use the machines."

To use the machine, a purchaser simply puts money in, fills out the policy and puts the policy back in the machine. The machine "grabs" one part of the policy; the buyer keeps the rest and mails it to Mutual of Omaha from the airport.

According to O'Connor, Mutual of Omaha has paid insurance claims to two victims of the 1977 Tenerife runway crash in Spain and two in the 1979 Chicago O'Hare crash. Passengers on both flights had taken out machine insurance before their fatal crash.

Nervous about flying after reading about insurance? You needn't be -- flying is still considered one of the safest ways to travel.

Still, some of the clauses can be mildly disquieting to read:

"If, during the trip . . . you disappear because of an accident . . . and your body has not been found within 52 weeks after the accident, it will be presumed, subject to no evidence to the contrary, that you suffered loss of life as a result of covered injuries."