Philippines.Clark Air Base · fighter pilots see a trail climb and level off

Around noon on September 8, 1949 (04:00 GMT), a flight of three F-51 Mustang fighters of the 67th Fighter Squadron was flying at about 6,000 feet, some ten miles (16 kilometers) southwest of Clark Air Base on the Philippine island of Luzon. It was led by the squadron commander, Major Louis J. Sebille. During a turn, his left wingman, Lieutenant R. J. Semrau, called on the radio: "Look up to the right." Sebille saw an object climbing toward the north at high speed, at an angle of about 30 degrees, leaving a condensation trail. He estimated it to be at about 15,000 feet and some 30 miles (nearly 50 kilometers) away, reversed his turn and spread the flight to follow it.

His signed statement is precise. In the minute or minute and a half it took him to come around to the north, the object reached about 50,000 feet. It was dark, and at that distance nothing more than a black dot could be made out. At that height it "made a sharp level-out not at all like an airplane leveling off after the climb," leaving a clear "elbow" in the trail. "My first impression was to start after it but obviously its speed was so great it was impossible." The trail was a thin line that, all along its course from the south, had not dissipated at all. From the separation it was gaining, he estimated it was traveling at "well over 800 miles per hour."

Lieutenant R. R. Crew, the other wingman, told the same story: he saw the trail climb at 30 degrees, a slight course change in which the trail "curled in," and the level-off between 35,000 and 40,000 feet; he never saw what made it, and at 12:20, already on the ground, he could still see part of the trail. Semrau, who saw it first, wrote in his signed statement that he saw "a black spot giving a smoke trail which appeared at first to be a sky-writer"; he was the only one besides Sebille to make out that spot. A fourth pilot, Lieutenant F. S. Welch, returning from a gunnery mission some 20 miles (32 kilometers) north of Clark, saw a very dense trail climbing north and leveling off at about 50,000 feet.

The fifth witness was on the ground. Lieutenant Harry C. Moore saw from the base service station the trail coming from the south, from Floridablanca, passing over the west side of Clark with a slight turn to the left and continuing north, above, he reckoned, 30,000 feet. And he added a decisive detail: that same morning he had flown from 08:00 to 11:45 at between 20,000 and 30,000 feet, and neither he nor the intercept aircraft he saw at 25,000–30,000 feet were leaving trails. The report also records the winds aloft, the weather (high cirrus and scattered cumulus) and the absence of test launches: the air attaché in Manila, the Navy, and the Philippine Army and Air Force all replied in the negative.

The duty intercept controller (the officer guiding the fighters by radar from the ground), Lieutenant Donald E. Williams, offered the simplest explanation: he had two F-51s at 30,000 feet that had left the base at 11:35 heading north to calibrate the radar, and he believed the trail was theirs and had formed late. On October 4, the intelligence section of the Far East Air Forces command closed its supplementary report rejecting that idea: thirty minutes had passed between those aircraft leaving the base and the sighting, and only one trail was seen, not two. "This section is unable to discern what object or phenomena caused the above mentioned con-trail."

The same file holds the statements of the two pilots of that calibration mission, Captain Malcolm B. Eden and Lieutenant Ernest Ball, which undercut the explanation from another side: by their account they took off at 10:10 and climbed to 25,000 feet over the base before being given a northerly heading (the controller's 11:35 is when they left the base, not when they took off); at 30,000 feet they continued to some 120 miles from the base, were given a heading of 170 (roughly south) back from there and landed at 12:40; and both signed that "while we were flying at 30,000 feet we did not see any vapor trails."

The report adds that the radar did not pick up the object, that the controller saw no other aircraft at that altitude and that no commercial, private or military flights were scheduled in the area. Years later, when the case was transferred to a Blue Book card, the conclusion was the opposite: "Other (contrail)," with the investigating officer's opinion that the two F-51s had left it, which, like the controller, it has leaving the base at 11:35.

The file brings together five officers from the same squadron, four of them pilots in the air, with signed statements, wind and weather data, and an inquiry among the military services in the area. Louis Sebille, the main witness, died a year later in Korea, on August 5, 1950, diving his damaged aircraft into an enemy position, and was posthumously awarded the Medal of Honor, the Air Force's first of that war.

The file records an official disagreement. In 1949, the Pacific air command's intelligence studied the F-51 explanation, rejected it with two concrete arguments (the half-hour gap and the single trail) and admitted it did not know what it had been. Blue Book, in filing the case, adopted exactly the rejected explanation without new data. And the file holds more evidence against it than the 1949 report itself pointed out: the two pilots of those F-51s stated that they saw no vapor trails, the file does not place them south of Clark, where the trail came from, at the time of the sighting, and they were flying at 30,000 feet, below the level-off the witnesses describe; Lieutenant Moore, for his part, saw nobody leaving trails between 20,000 and 30,000 feet that morning.

Even so, the case does not necessarily point to anything strange. Judging the height, distance and speed of a distant dot is very difficult, and an aircraft approaching high and straight can seem to climb as its trail forms in front of the observer. A jet or high-altitude aircraft not in the base's records (from another service, in transit or from another country) would produce a trail like this, although no source proposes one and the report records that neither the radar nor the controller saw another aircraft and that no flights were scheduled in the area; Sebille's "well over 800 miles per hour" and the "well over 1,000 MPH" that the intelligence report enters under speed, without saying whose estimate it is, are above the aircraft of the day, but they are guesses by eye.

Nor do the statements of Moore and the calibration pilots settle it: they refer to 30,000 feet or below, and the witnesses put the level-off between 35,000 and 50,000; the trail also persisted for more than half an hour, like a condensation trail. And Eden and Ball's "we did not see any vapor trails" also means the only aircraft at altitude that morning did not see the one the five officers described. That the file refutes the only explanation put forward does not prove there is none: it leaves the case without an identified cause, with a maneuver, the sharp level-off, that three pilots describe separately.