After an intensive planning, maintenance, and briefing period, the mission was scheduled for January 1, 1967. Poor weather caused a 24-hour delay, but even then, a solid overcast covered the North Vietnamese airbases at Phúc Yên, Gia Lam, Kép, and Cat Bai when the bogus strike force began arriving over the target area, five-minute intervals separating the flights of F-4s. Leading the first flight, Olds overflew the primary MiG-21 base at Phúc Yên and was on a second pass when MiGs finally began popping up through the cloud base. Although at first seemingly random in nature, it quickly became apparent that the MiGs were ground-controlled intercepts designed to place the supposed F-105s in a vise between enemies to their front and rear.