Las Vegas Air Force Station, Nevada: Radar tracks 6,200 mph target that stops, answers IFF
On July 16, 1957, at 1:56 p.m., radar operators at Las Vegas Air Force Station on Angel Peak, Nevada, tracked an inbound target at about 6,200 mph that stopped and remained stationary for 12 seconds north of the Grand Canyon before departing at about 7,000 mph; the target answered encrypted military IFF signals.
Background
At 1:56 p.m., 1st Lt. Clifford E. Pocock, scope operator A2C Walter Lyons, and control technician A1C Armand Therrien at Las Vegas Air Force Station on Angel Peak, Nevada, were using the FPS-3A L-band search radar when they tracked an inbound target at about 6,200 mph. The target 'stopped abruptly' and 'remained stationary' for 12 seconds to the east-northeast, 85 miles away, north of the Grand Canyon in Arizona. It then headed outbound at about 7,000 mph and disappeared at the radar's maximum range of 224 miles, near Marble Canyon, Arizona. The target responded to encrypted military IFF transponder signals and transmitted encrypted responses. The case is listed among the Project Blue Book unknowns and documented by NICAP, Brad Sparks, and Jerome Clark. The account follows the entry in George M. Eberhart's chronology UFOs and Intelligence (CUFOS) and the sources cited there; it is not an independent determination by From Beyond Space.