This document contains briefing material prepared for Mr. Walter N. Elder, Executive Assistant to the Director of the Central Intelligence Agency (CIA), regarding a November 19, 1964, incident allegedly involving unidentified aircraft in the vicinity of Puerto Rico. The previous entry in this collection, CIA-UAP-D022, contains CIA memoranda on the same subject matter. The briefing includes additional details regarding that incident, including a characterization of the meteorological conditions and sensing capabilities of nearby U.S. military collection systems. The briefing states that a radar system aboard USS Gyatt, a guided missile destroyer operating in the vicinity, detected a contact tracking more than 3,800 knots (approximately 4,373 mph) over a period of 21 minutes. The briefing contains visual estimates regarding the phenomenon’s apparent capabilities from the pilot of an F-8 Crusader who was present during the incident.