On July 17, 1957, a US Air Force RB-47 underwent an extraordinary experience now considered one of the classic radar/visual UFO sightings.
Equipped with electronic intelligence (ELINT) gear, the aircraft left Forbes Air Force Base, Topeka, Kansas, on a multipurpose mission that included gunnery, navigation, and electronic countermeasure (ECM) exercises. Three of its six-man crew were electronic-welfare officers who ran the ECM equipment.
In the early morning hours, the first two parts of its mission completed, the RB-47 was returning over the Gulf coast near Gulfport, Mississippi, when Frank B McClure, who was manning the second ELINT station (of three aboard the aircraft), noticed a signal at 3000 megahertz (MHz) frequency at five o'clock relative to the plane's position. McClure initially assumed the signal was coming from a ground-based radar, but then it moved upscope, crossed the RB-47's flight path, and descended downscope on the other side. ELINT station #1 was not working the frequency at the time, and station #3 was incapable of operating on that frequency at any time. Though puzzled, McClure said nothing, assuming that there must be some mundane explanation.
Near Meridian, Mississippi, the plane turned west, travelling at 34,500 feet and 500 mph. Soon afterwards, at 4:10 am., over east-central Louisiana, Major Lewis D Chase, the pilot, saw an intense blue light at eleven o'clock. He called it to the attention of his co-pilot, 1st Lieutenant James H McCoid, and the two watched the light moving rapidly toward them. Then immediately notified the crew that evasive action would have to be taken, but before that happened, the object instantaneously changed direction and streaked in front of them, disappearing at two o'clock.
Remembering the odd signal he had received some minutes earlier, McClure set his equipment to scan the 3000 MHz range and found he was getting a strong signal from the plane's two o'clock position. A check of the #2 monitor on known ground-radar stations indicated it was functioning perfectly, and the signal also appeared on the #1 monitor, run by John J Provenzano. The possibility that an unknown ground-radar station was responsible for the signal was eliminated when the signal moved gradually upscope - not downscope, as it should have if its source were on the ground - even as the RB-47 continued on its westward path at 500 mph.
Now the plane and its crew were in east Texas, within the radar-coverage area of an Air Force radar unit (codenamed "Utah") in Duncanville. The aircraft's occupants were growing ever more uneasy about their enigmatic companion. At 4:39 the pilot saw a "huge" light 5000 feet below him at two o'clock. Though he could not prove it, he had a strong sense that the light was on top of a larger object. A minute later McClure at ELINT #2 reported two signals at 40 and 70 degrees. The first UFO was at the latter location, and now both Chase and McCoid spotted another object at the former site. The second UFO was visible only briefly.
Chase notified Utah and asked for all possible assistance as he left his flight path and headed toward one of the UFOs. It was now 4:42, and ELINT #2 had one signal at 20 degrees' bearing. When Chase accelerated to 550 mph, the UFO pulled away. Seconds later McClure had two signals again at 40 and 70 degrees, and a minute and a half later only one, at 50 degrees. Utah asked Chase to tell it where the UFO was, and when he reported its location (10 miles northwest of Fort Worth), Utah picked it up immediately on its radar scopes. At 4:50 the UFO seemed to stop suddenly, and the RB-47 flew past it. At this moment it disappeared from the scopes, and ELINT #2 lost the signal.
Later, when interviewed by University of Arizona physicist James E Mcdonald, Chase (in McDonald's paraphrase) recalled that there was simultaneity between the moment when he began to sense that he was getting closure at approximately the RB-47 speed and the moment when Utah indicated that their target had stopped on their scopes. He said he veered a bit to avoid colliding with the object, not then being sure what its altitude was relative to the RB-47, and then found that he was coming over the top of it as he proceeded to close. At the instant that it blinked out visually and disappeared simultaneously from the #2 monitor and from the radar scopes at the site in Utah, it was at a depression angle relative to his position of something like 45 degrees.
Chase began a turn over the Mineral Wells, Texas, area, to get back on his original flight path, which would take him north in the direction of Forbes AFB. Suddenly the light reappeared behind them, and the instant it did, Utah and ELINT #2 were documenting its presence. The RB-47 again moved toward the UFO, getting within five nautical miles of it before it dropped to 15,000 feet, blinked out, and again vanished both visually and electronically.
At 4:55, concerned about his fuel situation, Chase notified Utah that he had to get back to Forbes. Two minutes later, at 300 degrees' bearing, McClure picked up a signal, and at 4:58 Chase observed the UFO 20 miles northwest of Fort Worth. The UFO trailed the aircraft, all the while emitting signals picked up by ELINT #2 until the object and signal disappeared over Oklahoma City at 5:40. The UFO and the RB-47 had kept company for 800 miles.
Both Project Blue Book and Air Defense Command Intelligence investigated the incident shortly after it occurred, though no account of it appeared in print until the publication, 12 years later, of Scientific Investigation of Unidentified Flying Objects, informally and better known as the Condon report. (Physicist Edward U Condon headed the Air Force-sponsored University of Colorado UFO Project (the "Condon Committee") between 1966 and 1969.) Committee investigator Gordon David Thayer, a physicist and radar expert, declared the case unexplained and later characterized the official Blue Book explanation (that the "UFO" was an airliner) as "literally ridiculous."
Subsequently, McDonald interviewed all six crew members, uncovered official records unavailable to the Condon Committee, and corrected some errors in Thayer's version (principally the date, which Thayer had as September 20). Despite a convoluted reinterpretation by debunker Phillip J. Klass, who speculated that a complex series of radar errors and the fortuitous appearances, consecutively, of a meteor, the star Vega, and an airliner were responsible for the event, the incident remains as puzzling today as it was in the early morning hours of July 17, 1957.