At 1215 mountain time, a Christen Industries Pitts S-2B crashed in a field three miles north of Longmont, killing the pilot and passenger. Witnesses said the airplane was in a vertical climb, ran out of airspeed, nosed over and came down in a spiral. They also reported hearing the engine surging, then fail. The airplane had departed about 2:15 earlier, and the endurance of a Pitts S-2B with full tanks is about 1.7 hours, but there was no preliminary information about a fuel stop.