On March 2, 2002, approximately 0620 Pacific standard time, a United Airlines Boeing 757-200, N589UA, was impacted by the boom of a deicing truck while it was standing in position on the ramp with the engines running. The airline transport pilot, his first officer, the four flight attendants, and the 83 passengers were not injured, but the aircraft sustained substantial damage. The 14 CFR Part 121 scheduled domestic passenger flight, which was preparing to depart for O'Hare International Airport, Chicago, Illinois, was being operated in visual meteorological conditions. The crew had filed an IFR flight plan. There was no emergency evacuation. According to United Airlines, the aircraft had been pushed back about 20 feet from the gate in order to remove heavy frost prior to taxi for departure. The deicing truck, which was being manned by a driver and a boom operator, had just completed deicing procedures when the accident occurred. Reportedly, the driver of the deicing truck, which had been parked just aft of the left wing and nose-in perpendicular to the fuselage, inadvertently turned his steering wheel in the wrong direction as he attempted to back away from the aircraft. In so doing, he allowed the deicing boom, which is mounted on the back end of the truck, to impact the trailing edge of the left aileron. The boom penetrated the aileron's structure to a depth of almost two feet, and damaging its spar. The boom operator, who was in the basket at the time of the impact was not injured. The deicing truck was not damaged. According to United Airlines Flight Safety, the area was well lighted, there were no ramp space constraints, and there was no apparent distractions or rushing.