1. DATE - TIME GROUP 2. LOCATION 13 Feb 53 14/0258Z San Francisco, California 3. SOURCE 10. CONCLUSION 3 Civ. men WEATHER PHENOMONA 4. NUMBER OF OBJECTS Report of objects attributed to effects of inversion in area One 5. LENGTH OF OBSERVATION 11. BRIEF SUMMARY AND ANALYSIS 22 Minutes Round black object followed by 2 silver streaks appearing to 6. TYPE OF OBSERVATION be vapor trails traveled at a high rate of speed maneuvering Ground-Visual up and down on zig zag course. A throbbing sound was heard 7. COURSE as the obj passed overhead at alt of approx 10,000'. Thousands of persons observed similar obj on 13 Feb 53. An 8. PHOTOS astronomer said that sightings were result of a temperature □ Yes inversion. ☒ No 9. PHYSICAL EVIDENCE □ Yes ☒ No