What a terrible tragedy Sunday in Lexington, Ky.

As a former air traffic controller, I was pretty much glued to the TV that morning, especially after hearing early speculation that the pilot may have attempted to depart from the wrong runway, one that only afforded him half the distance he needed to get his aircraft airborne.

I wondered, as I watched reports that day, what could have gone wrong?

I don’t know how many of you are pilots, or know that much about aviation, but here are a few things I thought might be helpful in understanding this disaster.

Runways are numbered based on a compass rose, or the 360 degrees that make it up. So, if you are departing due north, heading 360 degrees, you are on runway 36. The ‘0’ is dropped from the runway number. Runway 27 is 270 degrees, due west, runway 18 is heading 180 degrees, due south, and so on.

This pilot left, or attempted to leave, on runway 26, a heading of 260 degrees, instead of runway 22, 220 degrees. Unless his compass n and I assume the pilot’s wasn’t the only one in the aircraft n was inoperable, it would have shown him heading 260 degrees as he lined up on the runway.

Secondly, every runway has large black boxes on either side, with numbers on them that indicate in thousands of feet how much runway is remaining. They are also lighted when the runway light are activated so they can be seen at dawn, dusk and during the night.

The first one this pilot should have seen, assuming the lights were working, was a ‘3,’ which would indicate only 3,000 feet of runway remaining. Then he would have seen ‘2’ and ‘1.’

Had he been on runway 22, with 7,000 available, he would have seen ‘7,’ ‘6,’ and so on as he rolled down the runway.

There has been some question as to why there was only one air traffic controller in the tower at that time. That isn’t unusual. When I worked in Allentown, Pa., our midnight shift was always one fully qualified controller. Traffic was light, almost non-existent, and that one person could do it all.

At 7 a.m., a new group of controllers would arrive to relieve him or her.

In the Lexington crash, this was probably standard operating procedure for that time of day n the aircraft was cleared for takeoff just after 6 a.m.

I don’t know what the line-of-sight from the tower to the runway is at the airport, but in the dark, it is difficult to determine exact positions of an aircraft with only its exterior lights operating. Because runways 22 and 26 are so close together, it could have appeared as though the jet was on the correct runway.

In most cases, the controller watches all aircraft land and takeoff, assuming they are not distracted by other aircraft or other duties. Perhaps in this case, after clearing the jet for takeoff, the controller may have diverted his or her attention to the administrative duties of the job, including entering a departure time into the computer, or dealing with other planes requesting his or her services. I just don’t know.

There appears to be many questions surrounding this accident, which will take some time to sort out. Why the wrong runway? Was the flight crew rushed to make a departure time that would get them into Atlanta on time, as opposed to a ground delay in Kentucky? Were the lights activated on runway 22 or 26, or both? Had the pilots ever flown out of this airport, and if so, how familiar were they with the setup? Didn’t the pilots see the runway-remaining markers indicating how many feet were left?

Unfortunately, sometimes it takes a tragedy like this to bring problems with the system to light. In this case, there will probably be directives issued through the Federal Aviation Administration on pilots and controllers confirming runway assignments, or even double confirming them before aircraft begin their takeoff roll.

That isn’t much comfort for those whose loved ones perished in this crash, but if it can stop another one from occurring down the road …