All but the last observation in this series suggested a balloon flight, but a quick check with the weather stations in the area failed to turn up any record of a routine launching. Air Force investigators knew about the Skyhook project and could have obtained information on secret launchings, even though it was classified. But, since many of the investigators in these early days of the saucer era were more than half convinced that the unknown had been an interplanetary vehicle, they abandoned the inquiry at this point and officially labeled the case an Unknown. Flying-saucer addicts pounced on this conclusion as proof that the object had actually been a spaceship, that the Air Force knew it to be a spaceship and was deliberately concealing the news from the public. _A Probable Solution of the Mantell Case_ Although the case remained unsolved for nearly four years, the original analysis of the evidence, carried out by Dr. J. Allen Hynek, scientific consultant for the Air Force, made certain facts clear from the beginning. The final sightings in Ohio, so inconsistent with the general pattern of the other observations, obviously were not related to the reports from Kentucky and Tennessee. The object seen at Columbus had undoubtedly been the planet Venus, glowing brilliantly on the sunset horizon (see _Chapter_ IV). But the object that traveled southwest over Kentucky and Tennessee had almost certainly not been Venus. At least two objects--balloons or other aircraft--must be involved. It was possible, though not probable, that the unknown over Godman Field had been the planet Venus, or it might have been still a third object. The senior author of this book, after studying the facts available at the time and analyzing the weather conditions prevailing that winter afternoon, suggested that the object could have been a “mock sun” created by ice crystals in the cirrus clouds at high altitudes[III-3, p. 22]. The final solution of these UFO mysteries often depends on one key fact. Without it, the puzzle may never be solved. With it, all the pieces fall into place. The “mock sun” theory (see p. 244) remained the most probable explanation until, some time after the Skyhook project had been declassified, ATIC investigators discovered the key fact: At the time of the Mantell crash, the Clinton County Air Force Base, in southern Ohio, had been a launching site for Skyhook balloons. Unfortunately records for the day of Captain Mantell’s death were not available, and the men who had worked on the balloon project could no longer remember whether they had launched a Skyhook on that particular day. If an unacknowledged balloon had been in the area, however, only one more piece was needed to complete the puzzle: What path would the balloon have followed?