In spite of the vibrations, the defective engine was fitted to the aircraft, it being argued that the vibration level was "below acceptable standards." Before the flight to New York the aircraft was checked by mechanic Zdzislaw Yarmonyakom, who found that the No.1 engine had a defect in one of the turbine blades. This deformation was located in the lowest (and widest) part of the blade. The mechanic wanted to report it, but found that the defect was already marked there, and the plane was subsequently allowed to fly. As he later explained to investigators, the mechanic decided that the defect was within tolerance. Engine No.3 had 8200 hours operating time without repair. The aircraft was allowed to fly to New York with three engines and only the No.4 engine was fully serviceable.