Aviation pioneers once flocked to L.A.'s clear skies.

In January 1910, Los Angeles played host to the nation's first air show, a 10-day affair held on a dusty expanse in Dominguez Hills. Aviators, engineers and flight enthusiasts from all over the world attended the exhibition, where they watched pilots compete in endurance, speed and altitude contests.

But the real attraction proved to be Los Angeles itself.

The air was clear and dry, the sea breezes light and manageable. Engineers discovered that manufacturing could be done outdoors. And pilots learned they could rely on some 350 clear days a year.

It wasn't long before Los Angeles became the center for this growing corps of aircraft pioneers.

"The climate was ideal for both making planes and flying them," said Leonard Pitt, author of "Los Angeles A to Z: An Encyclopedia of the City and County" and a professor of history at Cal State Northridge. "It was natural that the aircraft industry would grow out of those conditions."

In these early days of aviation, Douglas, Martin and Northrop were not the names of multi-billion dollar corporations, but daring dreamers who wound up in Southern California.

"They loved aviation, but they didn't know much about it," said historian John Underwood. "They weren't real engineers - they were eyeball engineer. You had to be a good guesser to design an airplane in those days."

Perhaps the best of those guessers was Donald Douglas who, with an engineering degree from MIT, was by far the most technologically savvy of the early aircraft entrepreneurs.

Douglas had been hired by mechanic and aviation buff Glenn Martin, and followed his boss back East when demand for aircraft exploded during the First World War. Martin, who found deep-pocketed investors in Cleveland, never returned.

But in 1920, Douglas did. With $1,000, he set up his own shop in the back of a Santa Monica barbershop. And from those inauspicious beginnings, Douglas Aircraft Co. began developing a series of innovations that transformed the aircraft industry - including the first airplane to fly a load greater than its own weight, the first 12-seater passenger plane and the first all-metal-frame planes.

Other entrepreneurs also were getting busy. Allan and Malcolm Loughead, two brothers who had been building planes in a garage on the beach in Santa Barbara, founded Lockheed Aircraft Corp., setting up shop in North Hollywood before moving to Burbank, where it became the city's economic powerhouse.

In 1932, industrialist/aviator/movie producer Howard Hughes formed an aircraft division within the Hughes Tool Co. And in 1939, a former Lockheed engineer named Jack Northrop - who designed Lockheed's first airplane, the Vega, which was favored by, among others, Amelia Earhart - left to form his own company, Northrop Aircraft Corp., in Hawthorne.

With the start of World War II in Europe, Los Angeles was the nation's leading center of aircraft assembly and doing brisk business supplying the armed forces of the Allied countries.

This activity only intensified after Pearl Harbor in 1941, when the region's aircraft industry went into high gear. "Southern California became the Pittsburgh of aircraft production," says Pitt.

With orders for airplanes soaring, large amounts of capital were invested in the region, new plants were built and old factories were expanded. Thousands of laborers, skilled and unskilled, poured into Los Angeles from every state in the union.

Lockheed alone hired some 90,000 workers, producing 10,000 P-38 Lightnings and almost 3,000 B-17 bombers. Douglas produced 10,000 of its two-engine C-47 aircraft.

After the war, the industry went into a brief decline. But fortunately for local manufacturers, a new conflict - the Cold War - emerged, and the aircraft industry was replaced by something known as "aerospace," which grew to peaks unknown even during the wartime boom years.

As the industry added electronics to its capabilities and shifted its emphasis to the space race with the Soviet Union, old aircraft firms revolutionized and new organizations entered the picture.

A pair of Caltech engineers, Simon Ramo and Dean Woolridge, for example, joined Hughes and brought that firm to the forefront of electronics technology by developing radar, which enabled pilots to detect targets in bad weather even at night, and to precisely fire guided missiles under such conditions. Soon, more money was being spent on the electronics of a plane than on its airframe.

Lockheed's clandestine "Skunkworks" facility in Burbank, founded by Clarence "Kelly" Johnson in 1943, produced U-2 and SR-71 spy-planes.

"It put this area on map as far as the nuclear arms race," said Les Copeland, president of the Burbank Aviation Museum. "These are the planes we sent over Russia, Nobody's missiles could get high enough to catch them."

L.A.'s research institutions, such as Caltech's Jet Propulsion Laboratory, and the Rand Corp., founded at Douglas during the war, also began playing a much larger role in the industry.

For the three decades after World War II, the aircraft-missile-electronics complex was the foundation of the region's economy. At its peak in 1967, it employed about 500,000 people, nearly 43 percent of the region's total manufacturing employment.

But when the Cold War ended, so did the need for such a massive defense infrastructure. The region endured massive job losses, as well as the loss of its locally-based corporate headquarters in a wave of consolidations that has been sweeping the industry.