"Cessna Six Zero Nine Six Golf, taxi into position and hold."

I remember the time, now 15 years ago, that I first heard those words as I awaited a takeoff clearance from the tower at the Raleigh-Durham Airport. I remember also being struck by how nervous my flight instructor became.

"This is a stupid practice," he said to me as we stopped the two-seat airplane in takeoff position. "Here we are, in the middle of the runway, with no way to see what's coming behind us, and we're totally dependent on someone we don't know to keep us from getting hit."

That apprehension must have hung in the cockpit of a Sky West commuter plane as it sat for almost two minutes on the runway at Los Angeles International Airport, waiting for a takeoff clearance that never came. A USAir Boeing 737, having been cleared to land, slammed into the commuter, killing 12 aboard the smaller plane and 22 aboard the jet.

A lot of things are being questioned about the crash: the need for flame-retardant materials in the cabin, the development of reliable ground radar to show controllers where planes are on the airport runways and taxiways, even the airport designs that sometimes restrict a controller's visibility from the tower to the runway.

One thing is certain, however. The Los Angeles crash could not have happened without a controller's having ordered the Sky West commuter onto the runway and prohibiting it from taking off without further clearance. That practice clearly will be examined, and it will be a good thing if the Federal Aviation Administration should decide to put some pretty strict limits on it.

To be sure, the procedure has its uses. It stretches an airport's capacity to handle takeoffs and landings. Having a plane waiting in takeoff position for another plane to get out of the way can shave 10 to 15 seconds off the time needed for a takeoff. When crowded airports often have as many as 100 or more arrivals and departures every hour, those extra 15 seconds translate into thousands of additional landings and takeoffs each year.

The problem is that some controllers can't judge the difference between what's safe and what isn't. If anecdotal evidence is any guide, the problem is very much alive here at Washington National Airport, where in the past year I have been in three commercial airliners that taxied into takeoff position only to be ordered off the runway to make room for a plane that was coming in for a landing.

Controllers, of course, are human. They sometimes forget where a plane is or where it needs to go to keep the system working. On my last flight in a single-engine plane into Baltimore-Washington and Dulles airports a week ago, controllers at both fields momentarily forgot about me: I was directed to fly through the final approach course at Baltimore, and I arrived at the final Dulles approach about 2,000 feet too high. Those are minor mistakes, but they occur all too often. On almost every flight, I hear other pilots on my frequency reminding controllers of their position or their need to turn, climb or descend.

A controller's instruction, or clearance, carries the force of law. Federal regulations do give pilots an escape hatch, making a clearance a lot like a traffic light -- you can legally disobey it in an emergency. Had the commuter pilot known a jet was bearing down on the runway, he certainly would have gotten out of there. Likewise, had the USAir pilots seen the commuter plane on the runway, they would have broken off the approach.

In the Los Angeles crash, the controller directed the Sky West commuter plane onto runway 24 Left at its intersection with taxiway 45. The intersection is more than 2,000 feet from the approach end of the runway.

Shortly afterward, the controller cleared the USAir jet to land on the same runway. As the USAir pilots flew toward the runway, they were looking for two things. First, they were keeping an eye out for the lights of a moving plane somewhere along the runway. Second, they were looking for the lights of a plane at the end of the runway waiting to take off.

Even if the USAir pilots had focused on the exact spot where the commuter was parked on the runway, the lights of a small, stationary plane almost a half-mile down the runway would have been terribly difficult to see. The only rear-facing light on the Sky West commuter is white; it very likely blended in with the white lights embedded along the two-mile center line of the runway. The USAir copilot, who was flying the plane, told investigators he never saw the commuter. The jet had just touched down on its main landing gear, and the nose wheels were about to come down when everything went black, he said.

There are probably dozens of things that could have prevented the accident. The USAir crew could have asked the tower controller if the commuter plane was still holding. The controller, unsure of whether there was a plane holding on the runway, could have sent the USAir jet around for another landing just in case. The commuter pilots, sitting in the middle of the runway for more than a minute -- in what probably seemed to them like a lifetime -- could have asked for takeoff clearance.

For the pilots, however, not checking with the controller was an entirely normal course of action. The time of day, the position of the commuter far down the runway and the clearance of the USAir jet all contributed to the crash. Still, this shouldn't be treated as a freakish combination of improbable factors. The FAA needs to curtail a controller's power to clear planes into takeoff position at night or during times of low visibility or -- at the very least -- when an incoming aircraft is within a certain distance of touching down.

The writer is a member of The Post's Metropolitan staff. He holds a commercial pilot's license and has logged more than 1,000 flight hours.