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Today, black boxes -- which are actually painted bright orange or red -- are required on all airlines around the world and are built to withstand fire, heavy impact and intense water pressure. They have helped investigators examine many crashes and have led to immense improvements in airplane safety and pilot training. In recent years, the technology has been applied to boats, trucks and, increasingly, automobiles.

Dr. Warren was a young fuel chemist when he developed his invention in 1953, after being asked to help investigate the crash of one of the world's first jet airliners, the British-built de Havilland Comet. The crash in India killed all 43 people on board but was a mystery, Dr. Warren said, "without any explanation, without any witness, without any survivors."

The investigation struck a personal chord with Dr. Warren, whose father had died in an unsolved airplane crash off the southern coast of Australia 19 years earlier. His final gift to his son was a crystal radio set, and Dr. Warren retained his childhood interest in electronics long after he had become a chemist.

While investigating the de Havilland crash, Dr. Warren imagined a novel use for a small pocket recorder that he saw at a trade show.

"If a businessman had been using one of these in the plane," he said in 1998, "and we could find it in the wreckage and we played it back, we'd say, 'We know what caused this.' "

Dr. Warren tried to interest his supervisors in the idea but was told to stick to his examination of exploding fuel tanks. Nonetheless, he continued experimenting and by 1957 a prototype of the flight data recorder was ready.

"I couldn't get it out of my mind," Dr. Warren said. "It seemed so bloody simple."

The ARL Flight Memory Unit -- named after the Aeronautical Research Laboratories in Melbourne, where Dr. Warren spent most of his career as a research scientist -- could record four hours of instrument readings and pilots' voices on a steel wire. But Dr. Warren encountered widespread scorn from pilots and government officials in his homeland.

"It would be like having a spy flying alongside -- no aircraft would take off with big brother listening," an Australian airline pilots group said dismissively.

But in 1958, a British aviation official visiting Dr. Warren's laboratory was impressed with his invention and invited him to England, where other scientists and engineers helped build improved models and put the flight recorders into production. A reporter dubbed the device a "black box" because of its seemingly mysterious properties.

Some U.S. airlines began to use flight data recorders in the late 1950s. After a fatal airline crash in Australia in 1960, a judge recommended that the recording devices be installed on commercial aircraft in that country. Despite opposition from pilots groups, the recorders quickly caught on in other countries.