It is 18 years since the First Great International Paper Airplane Contest, and the aircraft industry is starting to catch up.

Time for another contest.

And so, this being Washington, they had a full-dress press conference at the Air and Space Museum, complete with an aerodynamics engineer from MIT who explained the principles of flight in 4 minutes 23 seconds.

It is not for fun, you understand. During the question period a reporter asked, "Why would grown men and women do such a thing?" The answer was that the event is to dramatize and possibly advance the revolution in aircraft construction.

On the other hand, museum director Walter J. Boyne admitted, fun is not officially prohibited.

Rules for the Second Great International etc. will liberate the paper-plane designers of the world, he said, just as composite construction discoveries have produced gliders that can soar for 900 miles and a plane that someday soon will fly nonstop around the world without refueling.

It seems that planes with half the weight and four times the strength of aluminum can now be made from carbon fibers glued together with epoxy and layered as thick as need be at stress points.

Accordingly, the new contest rules allow laminated paper, built up in glued layers to achieve rigid forms. But glue and cellophane tape cannot be used just to add weight. Other rules: Since the all-paper plane itself is the entry, it must have your name, address, phone number and throwing instructions written on it. Also the event and category.

There are four events: time aloft, distance, aerobatics and esthetic design (a doily will not do, Boyne warned -- it must fly for 15 feet or 3 seconds). Categories are: professional, nonprofessional and junior (under 14). Entries go to: International Paper Airplane Contest, Museum of Flight, 9404 E. Marginal Way South, Seattle, Wash. 98108. The Museum of Flight is a cosponsor of the contest. Deadline is May 1. Prizes include medals and a trip to Seattle. The winners will be exhibited at the Air and Space Museum alongside the Spirit of St. Louis and the Gossamer Condor.

Last time, 11,851 planes were entered by 5,144 adults and almost as many children in 28 countries. It was an international sensation. The winning time aloft was 9.9 seconds (10.2 for the professionals), and the winning distance was 58 feet 2 inches. The professional winner ran into a wall at 91 feet 6 inches.

But that's nothing.

One reporter mentioned an Air Force colonel who threw a paper plane 155 feet. And the Guinness Book of World Records cites a 15-second flight a decade ago in Nashville and an endurance flight of 1 minute 33 seconds in Tokyo in 1980.

"We're expecting 20,000 entries," said Boyne. Someone reminded him that the Academy of Model Aeronautics (we told you this was serious) alone has 100,000 members, so his estimate may be a bit modest.

At last came the moment the press had been waiting for: a class in paper airplane construction. In no time, darts of traditional schoolboy design were skimming through the air, while some technicians from cosponsoring Science 85 magazine shot off exotic craft with oval wings, ailerons, origami airfoils and needle noses capable of breaking the sound barrier.

Camera operators had Boyne throwing planes until his eyes glazed.

This was all very well, but the new technicians will have to go some to beat C.O. (Chick) Reinhart, the Chuck Yeager of paper aircraft, who threw a plane from a 10th story office window at 60 Beaver St., Manhattan, across the East River into Brooklyn for an all-time Guinness record of 1 1/4 miles.

That was in August 1933, guys.