Mock attacks by Soviet Air Force fighters begun in the air corridors to scare the American pilots caused great confusion and considerably increased the danger of air collisions. Also as many Yakovlev and Lavochkin fighters as possible were assembled around Berlin and then flown en masse in a westerly direction though the corridors. Near the western border of the Soviet occupation zone, they peeled off and flew along the zone border to the next corridor so they could fly back to Berlin along it, against the traffic, to their airfields around Berlin.