On June 3, 1995, at 1130 central daylight time, an Airbus Industries A320-211, N326US, operating as Northwest Airlines Flight 115, collided with a tug on the ramp at the Minneapolis- St. Paul Airport resulting in substantial damage. The crew of 7 and 108 passengers reported no injuries. The 14 CFR Part 121 flight was operating in visual meteorological conditions. An IFR flight plan was on file. The flight was originating at the time of the accident with an intended destination of Orange County, California. The Captain stated that after pushback from the gate he communicated with the pushback tug operator and then his attention was diverted to details inside the cockpit. When he looked out in preparation to taxiing he did not see the wingwalker or tug and "assumed" that he had received a "waveoff." As power was applied and the airplane began to move he heard a loud noise and applied the brakes to stop the airplane. He then realized that he had collided with the pushback tug.