Jerome F. Lederer, who was coaxed out of retirement in 1967 to become NASA's safety director, began a distinguished career in aerospace safety with the U.S. Air Mail Service in 1926 when, as a young aeronautical engineer, he was hired to do something about the appalling fatality rate for air mail pilots.

Thirty-one of the first 40 pilots were killed and one of every six was killed during the nine years the federal government ran the air mail service before contracting out to fledgling airlines in 1927.

During a recent interview, Lederer, 83, listed two things he learned during that job that apply as much to NASA now as they did to the air mail service then:

Schedule pressure is potentially fatal.

Tests of equipment must anticipate all possible uses.

"A major cause of these air mail fatalities was the psychological pressure on the pilots by post office officials," Lederer said. "There were few lighted runways, no radar weather reports and little weather information, but the post office insisted the mail go through."

In an attempt to learn what was happening, the Army crashed 16 airplanes into a concrete wall and took slow-motion movies. The movies showed that when the planes hit the wall, the fuel tanks split open and spilled gasoline onto the hot exhaust pipes that ran along the sides of the planes.

The solution: Exhaust each of the cylinders on the plane's engine individually, at the front, and drop the long exhaust pipe.

"We had done all our testing in the daytime," Lederer said, "and we flew at night. The first pilot up at night was temporarily blinded by the exhaust explosions on the engine in front of him." Although the pilot was able to land safely, that was the end of the no-exhaust-pipe experiment. "I learned you have to test in every possible operating condition," Lederer said.

Safety, Lederer said, is a poor term. He prefers "risk management" because "it is more realistic . . . . It gets away from the motherhood ambiguity of safety -- freedom from danger, a condition which rarely, if ever, exists."