On 24 September 1929, Lieutenant Jimmy Doolittle climbed into the rear cockpit of a biplane at Mitchel Field on Long Island, and somebody pulled a canvas hood over his head. From that moment he could see nothing outside. He could see only a handful of instruments on the panel in front of him.

He took off, flew a set course of about 15 miles, came back and landed on the same field, without once looking out. It was the first time anyone had flown a complete flight, from takeoff to landing, on instruments alone. Every airliner that lands in fog today owes something to those few minutes.

Why fog killed pilots

In the 1920s, cloud and fog were a death sentence for pilots who flew into them. The human balance system is simply not designed for flight: without a visible horizon, the inner ear happily reports that a steep, descending turn is straight and level flight. Pilots who lost sight of the ground tended to spiral into it, convinced to the end that their wings were level.

Airlines and the air mail service could not run reliable schedules if every bank of fog grounded the fleet, or worse. The Daniel Guggenheim Fund for the Promotion of Aeronautics, set up by the mining magnate Daniel Guggenheim to push American aviation forward, decided to tackle the problem head on. It created a Full Flight Laboratory at Mitchel Field and borrowed one of the Army's most capable young test pilots to run it: Jimmy Doolittle.

A documentary on the extraordinary life of Jimmy Doolittle, from racing pilot and engineer to wartime commander.

The instruments

Doolittle was more than a stick-and-rudder pilot. He held a doctorate in aeronautics from MIT, and he understood that the solution would come from better instruments, not braver pilots. Working with Elmer Sperry Jr., he helped develop a gyroscopic artificial horizon, which showed the aircraft's attitude against a fixed reference, and a directional gyro that held a steady heading where a magnetic compass would swing. Paul Kollsman, another Long Island engineer, provided a sensitive altimeter precise enough to fly an approach with.

Radio aids, developed alongside, helped guide the aircraft back towards the field. Together, these instruments told the pilot what the outside world could not: which way was up, which way he was heading, how high he was and where the runway was.

Under the hood

The aircraft was a Consolidated NY-2 Husky, a two-seat Navy trainer biplane, civil-registered NX7918. Doolittle sat in the rear cockpit, completely enclosed by a hood. In the front cockpit sat Lieutenant Benjamin Kelsey as safety pilot, ready to take over if anything went wrong. He never needed to.

Doolittle took off, flew out on a set course of about 15 miles, turned, came back and landed on Mitchel Field, all without seeing anything outside. The press was impressed. A contemporary magazine report, reproduced by the aviation history site This Day in Aviation, captured why this was different from earlier experiments.

Harry Guggenheim, the president of the fund that paid for the work, was even more emphatic. He announced that the problem of fog flying had finally been cracked.

From Mitchel Field to every cockpit

It was not quite solved, of course. It took years more work, better radio aids and a great deal of training before instrument flying became routine, and the instrument landing systems that guide modern airliners only matured after the Second World War. But the principle had been proved. A pilot who trusted good instruments over his own senses could fly, navigate and land without seeing the ground.

Doolittle went on to many other things: air racing records, the 1942 raid on Tokyo that bears his name, and command of the Eighth Air Force in Europe. Yet among aviators he is also remembered for this September day in 1929, when a man under a canvas hood showed that the sky did not have to be clear to be flown.

Biographics on the life and career of Jimmy Doolittle.

Instrument pioneers like Doolittle are the reason modern pilots train for hours "under the hood" before they are allowed to fly in cloud.

A short explainer on Doolittle's first instrument flight in 1929.

Sources: Wikipedia (Jimmy Doolittle), This Day in Aviation, Smithsonian National Air and Space Museum, Biographics