January 7, 1948 — Fort Knox, KY
1:45–3:50 p.m. A circular object is reported by civilians over Elizabethtown, Madisonville, Lexington, Maysville, Irvington, and Owensboro, Kentucky. In the Godman Army Airfield control tower at Fort Knox, Tech/Sgt. Quinton A. Blackwell and others spot an object shaped like an ice cream cone with a red light around the lower part in the southwest at 1:45 p.m. Base Commander Col. Guy Hix says it is about one-quarter the size of the full moon and white in color. The object maintains a constant angular position as seen from Godman as it apparently moves away at about 240–300 mph at an altitude of 50,000–60,000 feet.
Capt. Thomas F. Mantell Jr., a 25-year-old Kentucky Air National Guard pilot, and three others are flying F-51D fighters to Louisville, Kentucky. After Mantell reports his position to Standiford Field in Louisville at 2:50 p.m., Blackwell breaks in over the radio to request Mantell to intercept and identify the object. Mantell and two other fighters (piloted by Lieuts. Albert William Clements and B. A. Hammond), not equipped with oxygen masks, begin pursuit.
Flying at 300 mph and gradually climbing, Mantell gradually approaches the UFO from below. At about 3:10 p.m., in one of his last radio reports, Mantell says he is approaching 20,000 feet and the UFO “appears to be a metallic object or possibly reflection of sun from a metallic object, and it is of tremendous size” (although a later report corrects his transmission to “It’s above me and I’m gaining on it”). Two other F-51Ds quit the chase, no longer able to see Mantell or the object.
Mantell continues to perhaps 25,000 feet, blacks out, and crashes at 3:18 p.m. about 4 miles south-southwest of Franklin, Kentucky.
The UFO disappears from view behind a cloud at Godman at 3:50 p.m. The Project Sign staff, still not yet formally organized, are under pressure to come up with some kind of answer, so they quickly float Venus (offhandedly suggested by Ohio State University astronomer J. Allen Hynek) as an explanation. This implausible explanation is not even believed by the Air Force, but it remains unchallenged for several years. In 1952, Ruppelt reopens the case and identifies the object as a secret Skyhook balloon, although he cannot confirm a launch that day. Army veteran Clifford Stone finds later that there have been no Skyhook launches since late December.
However, Barry J. Greenwood and Robert Todd tentatively identify the balloon as one launched from Camp Ripley near Little Falls, Minnesota, on January 6. Researchers Francis Ridge and Brad Sparks declared in 2010 that there was sufficient doubt about the balloon explanation and other details to place the case back into the unidentified slot. [Eberhart]
Sources:
“Chase for Flying Disk Blamed in Crash Death,” Louisville (Ky.) Courier-Journal, January 9, 1948, pp. 1, 12;
“Flier Dies Chasing a ‘Flying Saucer,’” New York Times, January 9, 1948, p. 11;
“Did Airman Hit ‘Saucer,’ Fall to Death?” Nashville Tennessean, January 9, 1948, pp. 1, 4;
Donald Keyhoe, The Flying Saucers Are Real, 1950, pp. 15–21;
Harold T. Wilkins, Flying Saucers on the Attack, Citadel, 1954, pp. 89–92;
Edward Ruppelt, The Report on Unidentified Flying Objects, pp. 31–39;
Donald H. Menzel and Lyle G. Boyd, The World of Flying Saucers, Doubleday, 1963, pp. 33–39;
Loren E. Gross, UFOs: A History, 1948, The Author, 1988, pp. 2–8;
Timothy Good, Above Top Secret, pp. 262–263;
“The Mantell UFO: A Smoking Gun, Maybe!” Just Cause, no. 39 (March 1994): 9–10;
“The Mantell UFO: A Smoking Gun, Maybe! Part Two” Just Cause, no. 40 (June 1994): 8–12;
Christopher D. Allan, “The Mantell Case—50 Years Later,” IUR 23, no. 1 (Spring 1998): 7–9, 31–32;
Michael D. Swords, “Project Sign and the Estimate of the Situation,” JUFOS 7 (2000): 37;
Michael D. Swords, GrassRoots UFOs: Case Reports from the Timmerman Files, Fund for UFO Research, 2005, pp. 137–138;
Timothy Good, Need to Know, pp. 104–105;
Michael Swords and Robert Powell, UFOs and Government, pp. 51–52;
Brad Sparks, Blue Books Unknowns Catalogue, Case 69, pp. 30–31;
Jerome Clark, The UFO Encyclopedia, 3rd Ed., pp. 706–710;
Jerome Clark, The UFO Encyclopedia, 4th Ed., pp. 424, 773–776;
Greg Eghigian, After the Flying Saucers Came: A Global History of the UFO Phenomenon. Oxford University, 2024, p. 49;
Graff, Garrett M. UFO: The Inside Story of the US Government’s Search for Alien Life Here—and Out There. Avid Reader Press, 2023, pp. 37–39, 75–77;
Powell, Linda. Against the Odds: Major Donald E. Keyhoe and His Battle to End UFO Secrecy. Anomalist Press, 2023, pp. 61–63;
Flight Handbook, USAF Series F-51D Aircraft, January 20, 1954;
Wikipedia, “Mantell UFO incident”;
NICAP, “The Mantell Case”;
Center for UFO Studies, [clippings and case materials on Mantell case];
The Black Vault, [Mantell documents and photos];
“UFO Confrontation: Kentucky” segment of Sightings, Season 3, Episode 18, February 12, 1995;
“Mantell Re-Examined” segment of Sightings, Season 5, Episode 3, October 18, 1996;
Francis Ridge, The Mantell Incident: An Anatomy of a Re-Investigation, The Author, 2010;
“Captain Thomas Mantell UFO Encounter,” tinmon857 Youtube channel, October 24, 2011; [Sightings February 1996 segment]
“Sightings: Mantell UFO Incident (August, 1995),” Paranormal Videos You may have missed Youtube channel, May 11, 2017;
Kevin D. Randle, “The Mantell Analyses,” A Different Perspective, September 21, 2017;
“Captain Thomas F. Mantell’s Plane Crashed after Chasing a UFO over Kentucky on January 7, 1948,” Eyes on Cinema YouTube channel, November 30, 2023;
