Large disk observed by townspeople in large Mexican city

This is a second hand story.  I heard it from an old friend while I was in high school, which was 1960-64.  He had graduated fron UCLA engineering school, and was on vacation in (as I recall) Mexicali, Mexico, with a friend. The year was schetchy, but I know he said it was after the war had ended, and before 1958. Over the city plaza, a large disk, perhaps 200= feet across just appeared and hovered.  He and the friend noticed first that the town's people were jabbering and pointing in awe at this thing above them.
The disk was sivery, with noticable "portholes", and it  perhaps 200-500 feet above the plaza.  He was very impressed by it, for it darted suddenly over here to the left, then to the right, then in a moment, it dashed completely out of sight.
As a recent grad from engineering school, he knew that nothing he had ever seen or studied could possibly withstand that kind of forces of acceleration and maneuvering agility.  He concluded that it therefor must be extra-terrestrial.  He was guarded as he told us, for he didn't share the account for concern that others would think him to be crazy.  
Have you ever had any other reports of such a sighting in Mexico, above a city plaza?
Witness indicates that the date of the incident is approximate.  PD