Urner Liddel's Skyhook balloon explanation
From the UAP Encyclopedia, the open encyclopedia of UFO and UAP history · 🗓️ Event
Contents 7
| Date | 27 February 1951 |
|---|---|
| Topics | Beings & bodies (topic) |
| People | Urner Liddel, Thomas Mantell, Kenneth Arnold, Anthony Mirarchi, James E. McDonald |
| Testimony | Shellenberger testimony, p. 42 |
| Year | 1951 in UFO history |
| Timeline | 1951 on the UAP Timeline |
| Sources | 9 |
In February 1951 Look magazine published an article quoting Urner Liddel, chief of the nuclear physics branch of the U.S. Office of Naval Research, who said that essentially every credible flying saucer report could be explained by the Navy's giant "Skyhook" research balloons. The claim drew immediate pushback.[1][2]
The claim
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As reported by the Associated Press on 13 February 1951, Liddel said some 2,000 reports had been checked and that not a single observation could not be attributed to the cosmic-ray balloons. He described the balloons as about 100 feet across, rising to roughly 19 miles and carried by winds at up to 200 mph, and said he was convinced that a "saucer" photographed at 77,000 feet over Minnesota was a Skyhook. The balloons had been flown since 1947, he said, and reports had risen as more were launched; the project had been kept secret because of its connection with atomic work, but secrecy was no longer needed.[1]
A partial truth
Liddel's explanation had some basis. Skyhooks were huge plastic balloons that carried cosmic-ray instruments to great altitude and could look strange and metallic in sunlight, and a Skyhook is widely believed to have been what Captain Thomas Mantell was chasing when he died in January 1948. An Aviation Week editorial on 19 February 1951 praised Look for the story but called the revelation a tragic comment on government secrecy, arguing that a brief announcement could have prevented public alarm, wasted military effort and Mantell's death.[1][3]
Criticism
Critics said the explanation was far too sweeping. On 25 February former Air Force scientist Anthony Mirarchi called the Navy report erroneous, saying the green fireballs he had studied showed manoeuvring motion that balloons could not match. A Nairobi meteorological official noted that Skyhooks burst after about 30 hours and could not have reached East Africa. Atmospheric physicist James McDonald later reviewed the balloon explanation in detail and argued it fit only a fraction of good cases.[1][4]
Legacy
The article is often cited as an early example of an official effort to close the subject in public, and it came as the Air Force's own investigation, then called Project Grudge, was winding down.[2][5]
People and topics
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- U.S. Navy — The U.S. naval service, whose pilots reported the UAP encounters revealed in 2017.
- Unidentified anomalous phenomena — The U.S. government's current term for unidentified objects in the air, in space and underwater.
- Urner Liddel — Office of Naval Research physicist who said in 1951 that Skyhook balloons explained saucer reports.
- Office of Naval Research — The U.S. Navy's research funding office.
- Unidentified flying object — An object in the sky that can't be identified; the older term for UAP.
- Thomas Mantell — Air National Guard pilot who died chasing a UFO in 1948.
- Kenneth Arnold — Pilot whose 1947 sighting gave rise to the term "flying saucer".
- Project Twinkle — A 1949–51 Air Force effort to photograph the green fireballs over New Mexico.
- Anthony Mirarchi — Air Force scientist behind Project Twinkle who publicly challenged the balloon explanation in 1951.
- James E. McDonald — University of Arizona atmospheric physicist who campaigned for serious UFO research in the 1960s.
On the Timeline
- Dewey Fournet's motion study and Navy inquiry (1951) — A Blue Book officer reportedly runs a private, Navy-assisted inquiry into undersea and aerial UAP.
- Anthony Mirarchi's challenge to the balloon explanation (27 February 1951) — The head of Project Twinkle tells reporters the Navy is misleading the public and real UAP show controlled motion.
See every 1951 event on the UAP Timeline →
References
- "1951 newspaper and magazine items", Project 1947 · mail.project1947.com · archived copy
- Patrick Gross, French press on Liddel's claim (Feb 1951), UFOs at close sight · ufology.patrickgross.org · archived copy
- Skyhook balloon — Wikipedia · en.wikipedia.org · archived copy
- Patrick Gross, James McDonald's 1968 House statement on balloons, UFOs at close sight · ufologie.patrickgross.org · archived copy
- Project Grudge — Wikipedia · en.wikipedia.org · archived copy
- Skyhook balloon — Wikipedia · wikipedia.org · archived copy
- Green fireballs — Wikipedia · en.wikipedia.org · archived copy
- Green fireballs and Project Twinkle (Bruce Maccabee) — NICAP · nicap.org · archived copy
- babel.hathitrust.org · babel.hathitrust.org · archived copy
This page was last edited on 29 October 2026. Articles are written in our own words from the sources listed under References; disputed claims are attributed to the people who made them.
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