On 25 Aug 74, at 2207 hrs, US Air Defense radar detected an unknown approaching US airspace from the Gulf of Mexico. Originally the object was tracked at 2,200 (2530 mph) knots on a bearing of 325 degrees and at an altitude of 75,000 feet, a course that would intercept US territory about forty miles southwest of Corpus Cristi, Texas. After approximately sixty seconds of observation, at a position 155 miles southeast of Corpus Cristi, the object simultaneously decelerated to approximately 1700 (1955 mph) knots, turned to a heading of 290 degrees, and began a slow descent. It entered Mexican airspace approximately forty miles south of Brownsville, Texas. Radar tracked it approximately 500 miles to a point near the town of Coyame, in the state of Chihuahua, not far from the US border. There the object suddenly disappeared from the radar screens.
During the flight over Mexican airspace, the object leveled off at 45,000 feet, then descended to 20,000 feet. The descent was in level steps, not a smooth curve or straight line, and each level was maintained for approximately five minutes.
The object was tracked by two different military radar installations. It would have been within range of Brownsville civilian radar, but it is assumed that no civilian radar detected the object due to a lack of any such reports.
The point of disappearance from the radar screens was over a barren and sparsely populated area of Northern Mexico. At first it was assumed that the object had descended below the radar's horizon and a watch was kept for any re-emergence of the object. None occurred.
At first it was assumed that the object might be a meteor because of the high speed and descending flight path. But meteors normally travel at higher speeds, and descend in a smooth arc, not in "steps." And meteors do not normally make a thirty-five degree change in course. Shortly after detection an air defense alert was called. However, before any form of interception could be scrambled, the object turned to a course that would not immediately take it over US territory. The alert was called off within twenty minutes after the object's disappearance from the radar screen.
Fifty-two minutes after the disappearance, civilian radio traffic indicated that a civilian aircraft had gone down in that area. But it was clear that the missing aircraft had departed El Paso International with a destination of Mexico City, and could not, therefore, have been the object tracked over the Gulf of Mexico.
