AFTER ALL the technological gains made this side of the 20th century, it's no wonder that heads barely turn when an airplane flies overhead.

But it wasn't always that way. Less than 70 years ago, men in flying machines attracted huge crowds of onlookers. Then, cross- country aeroplane races began at the College Park Aviation Field (now College Park Airport) and stretched northwest to Chevy Chase and back. These events made headlines in all four of the Washington dailies and were logged in aviation history journals.

This Saturday and Sunday, College Park Airport, the oldest continuously operating airport in the world, will hold its 11th annual open house so visitors can get a free closeup view of those early days of aviation and a look at a modern community airport at work.

This year's open house features actor Kirby Grant, who starred in the '50s and '60s television series "Sky King." There'll be a host of planes on display -- antique and experimental aircraft, ultralights, a DC-3 cargo plane and helicopters. The Federal Aviation Administration, National Aeronautics and Space Administration, and Aircraft Owners and Pilots Association will also have exhibits.

On Saturday evening at 8, the Navy's bluegrass group Country Current will perform, followed at 9 by fireworks. The "Flying Circus" will perform both days at 3 p.m.

If you'd like a bird's-eye view of the airport, Washington's monuments, the Blue Ridge Mountains, the Chesapeake Bay or Saturday's Penn State game at Byrd Stadium, airplane and helicopter rides will be available for a nominal donation to the Friends of College Park Airport, sponsors of the open house.

The open house got off the ground in 1974, after neighboring communities in Prince George's County complained that the 76plane airport was noisy and dangerous.

"People felt that pilots were crazy daredevils and that the airport was unsafe," says Walter Starling, the chairman of the airport friends group and a WCLY/WPGC radio traffic reporter who flies twice daily from the airport.

"We decided to open the airport to let them know it is safe. It was developed as an educational weekend."

And there's plenty to learn about. One of the main attractions is the airport's museum, where visitors can explore aviation history.

Lining the walls are photographs of the Wright brothers, the inauguration of air mail service and the Berliner helicopter. Invented by Washington automobile dealer Emile Berliner and his son, Henry, it made made the first controlled helicopter flight there in 1924. (Emile Berliner also held patents on acoustical tile and the Gramophone, later marketed as the RCA Victrola).

On display are propellers and motors from biplanes, leather flight jackets, facemasks and goggles and a radio and transmitter rom a WWII Japanese Zero fighter.

A handful of vintage aviation movies are also shown continously. The museum is free but depends on donations. Normal hours are noon to 4, Friday through Sunday, but it will be open from 10 to 5 this Saturday and Sunday.

The airport itself has a colorful history. It got its start in 1909 when Wilbur and Orville Wright sold the Army its first plane, the "Miss Columbia," and then began flight instruction for two Signal Corps officers at the airport.

The lessons kicked off a series of aviation firsts at College Park. The year 1911 alone saw the first U.S. woman air passenger; the first Army aviation school; the first bombsight test; and the first lights for night landings.

The following year, Lt. Henry "Hap" Arnold, flying out of College Park, became the first to fly a mile high; the first airborne machine gun test was conducted over the field; and the first aviation accident to kill an enlisted man occurre there. The short, bumpy lane off Calvert Road that leads to the airport, Cpl. Frank Scott Drive, is named after him.

AIRPORT OPEN HOUSE -- Saturday and Sunday, 10 to 5. Admission and parking are free. From the Beltway, take the Kenilworth Avenue west exit and follow signs to Calvert Road. Information: 927-1909.