OSHKOSH, Wis. -- Air-traffic controller Michelle Wrobleski looked up in the sky and saw at least a dozen planes, bunched up like migrating geese. A few miles behind them were 15 or 20 more, all headed for the same place.

"I see three Cessnas, there's a biplane on your left side. Watch out for him," she barked into her radio. "Twin Commander, you need to make a left 360. You're too fast. White Bonanza, you're converging on a Cessna. Turn left NOW! There you go. Beautiful!"

To keep the airwaves free, the pilots acknowledge her rapid-fire orders solely by rocking their wings. So heavy is the traffic that three planes at a time land on the same runway.

"Orange aircraft, I don't know what you are, but you're orange," another air-traffic controller snapped. "Land on the green dot. Welcome to Oshkosh."

Once a year, about 12,000 small aircraft converge on Oshkosh, Wis., for one of aviation's most revered gatherings. So many prop planes, military jets, antique war birds, homemade experimental aircraft, plus the occasional 747 or Concorde, fly in for the seven-day air show that Oshkosh temporarily becomes the world's busiest airport. For this year's show, which ended Monday, the pilgrimage of pilots involved 19,000 takeoffs and landings over 10 days.

To get so many planes in and out, the Federal Aviation Administration suspends its normal air-traffic rules. That makes the show the all-star game for air-traffic controllers, a chance to test their skills under some of the toughest conditions imaginable. This year, the FAA picked 73 of its Great Lakes region's best controllers for Oshkosh duty.

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