Why did the airplanes come so close to each other? It was, the NTSB has concluded, simply an error. The controller, who has a history of employment problems according to several reports, cleared the ERJ to take off on Runway 14 shortly after he’d cleared the 172 to go on Runway 18. It never should have happened. But it did. Why it happened is a complicated question. The controller has said he thought it would take longer, between 3 and 5 minutes, for the Cessna to get airborne, which flies in the face of experience. I don’t know about you, but when I’m cleared for takeoff, it takes about 3 to 5 seconds for me to take the active and maybe 20 or 30 seconds to accelerate, rotate, and get to 300 feet. So, again, based on my experience, the controller’s estimate was off by a factor of 10. Not only that, but since when do controllers clear airplanes to take off on intersecting runways based on assumptions about how long it will take a pilot to get his act together? Actually, the controllers’ manual mandates that the second airplane can’t be cleared until the first one has passed the intersecting point. That didn’t happen. Not even close. Such errors are scary stuff. But, again, they happen.