The sky was at the mercy of the pilots yesterday as the Air Force brought out its best to celebrate the 50th anniversary of the air traffic controllers.

More than 20,000 people endured the 90-degree weather to gaze skyward as the planes -- sometimes three and four at once -- performed dives, twists and flips at the all-day air show on the grounds of the Simpson Middle School in Leesburg.

Al and Sharon Capps of Chantilly brought their two children and two of their neighbor's children along with a picnic lunch to the show.

"I like when the plane goes straight up in the air then comes diving down," said Jesse Capps, twirling himself around.

Tactical fighter pilot Doug Cochran was as excited as the spectators. "I like the combination of excitement, challenge and the flow of adrenaline," he said. "I like the feeling of giving air superiority with my machine.

"What divides a standard pilot from a fighter pilot is the ability to deal with a multi-bogey environment," Cochran said.

A bogey is a target or enemy aircraft.

Cochran said the air show flyers were the top men of their class in fighter school. "There are only three classes a year of five to six people in the F-15 program. The man flying the F-15, Capt. Tim Fyda, graduated first among all three of the classes," Cochran said.

Cochran, a tall, tanned flyer who is based in Hampton, Va., said flying was a childhood dream.

Many little boys shared that feeling; they watched the show clutching bags of information on how to be a pilot.

"Our sons begged to come here after seeing and hearing the planes fly over the house," said Paula Shatarsky of Leesburg. "I like the out-of-controls," said 4-year-old Adam, referring to the maneuver in which a plane appears to be out of control as it spins in the sky.

The planes also caused a stir at the home of Brenda and Richard Knop of Leesburg. "Our horses stopped eating and stuck their heads out of the barn to see what was going on," Brenda Knop said.

They brought their 5-year-old son, Clark, to the celebration. Wearing red sunglasses, Clark looked captivated by the planes while his father held him in his lap.

Bob Sturgill, program manager of the three-day anniversary show, said events are taking place across the country but that this one was the most elaborate.

Yesterday's celebration also featured equipment on display, souvenirs and brochures, and a free concert by the Air Force Airmen of Note orchestra.

The event continues today with an open house from 8 a.m. to 5 p.m. at the Washington Air Route Traffic Control Center on Rte. 7 in Leesburg.

During the early days of air traffic control, a flagman located in a visible area directed the planes. The first air control tower was commissioned by the federal government for Washington's Hoover Airport, which was replaced by National Airport.

Today, air traffic controllers at the Washington Air Traffic Control Center and the towers at National, Baltimore and Dulles combine to serve air traffic needs of more than 13,000 aircraft every 24 hours.