Unidentified white object at 40,000 feet

Summary

Three engineers in Minneapolis observed an object with a white vapor trail at high altitude. The object moved horizontally at about 900 mph before entering a vertical dive lasting 10-15 seconds. During the descent, the object glowed several times and then leveled off. The observers, using a theodolite from the General Mills lab, concluded it wasn't a conventional aircraft due to its speed and unusual maneuvers. There was no detectable sound and the vapor trail dissipated quickly. Although they considered the possibility of a jet aircraft, the observed characteristics didn't match typical behavior.