You seldom learn exactly what happened on a particular flight -- unless the pilot survives -- but you can imagine a plausible scenario. On the first approach, the pilot stops descending at the decision height and overflies the runway. Looking down, he glimpses the runway lights, and possibly, if the fog is spotty enough, even discerns illuminated features on the ground -- a pool of light around a windsock or in front of a building, airplanes parked on the ramp. After all, these things are only 200 feet away, and the visibility under the overcast is half a mile. It appears that with a little luck he ought to be able to land. So he comes around for another try.