United Flight 147 Mountain Home Sighting (1947)

Background

The summer of 1947 produced a national run of unexplained aerial reports. Kenneth Arnold's sighting near Mount Rainier in late June and the Roswell press release in early July set the tone, and the Army Air Forces and later the Air Force began collecting reports with growing urgency. Commercial airline crews were among the more notable witnesses because they were trained observers flying scheduled routes over populated areas. The Air Force's early investigative effort, Project Sign, began in late 1947; its successor, Project Blue Book, ran from 1952 to 1969 (Encyclopaedia Britannica). The Air Force's own history of these efforts is summarized by Ohio State University's Origins project.

In the weeks before August 1947, the Boise area had already drawn attention. The ACUFO case page lists two earlier airline reports near the city, by Capt. E. J. Smith (July 4) and Capt. Charles F. Gibian (July 20).

The sighting

According to the ACUFO account, which summarizes a report in The Boise Statesman of August 20, 1947, United Air Lines Flight 147 was flying from Salt Lake City to Spokane. Around noon, while at 8,000 feet and descending toward Boise near Mountain Home Army Air Base, the captain and co-pilot saw two silver, disc-shaped objects pass roughly 2,000 feet below them, traveling almost due south.

The captain estimated the objects were about five feet in diameter and compared them to skeet targets, describing their movement as effortless. The co-pilot timed them over about 15 seconds and estimated they covered four miles, which works out to roughly 960 mph. Both men reported the sighting to United's Boise staff. The captain asked that his name and his co-pilot's not be published. The newspaper described him as "visibly impressed."

The ACUFO page notes that this was the first airline report in the Boise series to give a definite distance and speed estimate. The aircraft type is listed as "quite likely" a DC-3, which the same page does not confirm.

Investigation and interpretation

The sighting was visual only. No photographs or sketches are cited, and the crew's distance and speed figures rest on altitude judgments and a single timing. ACUFO rates its reliability and strangeness at 2 on a 1-3 scale and concludes "possible extraterrestrial craft." That conclusion is the view of one catalogue author, not an official finding. The author argues that the fastest U.S. aircraft of 1947, the Bell X-1 at about 700 mph and the Douglas D-558-1 at about 651 mph, do not match the reported speed.

Catalogues differ on classification. J. Allen Hynek's listing, as cited by ACUFO, is "DD" (daylight disc). A NICAP-derived chronology by Francis Ridge files it as "Blue Book Unknown." The accounts I could access do not show whether the Air Force tested conventional explanations such as reflections, birds, or aircraft, or what its file concluded.

Significance

The case matters less for its physical details than for what it shows about the early reporting environment. Airline crews were seen as credible witnesses, and the Boise reports suggest that pilots were beginning to give the numerical estimates that investigators wanted. The sighting also illustrates how much of the early record depends on newspaper accounts and later secondary catalogues. Its details come down to a newspaper article and a crew's estimates, neither of which has been independently checked here.

The event is best treated as a documented report with an unresolved explanation. It belongs to the 1947 airline-sighting series that informed the Air Force's early work, and it remains a standard reference in catalogues of the period.