On March 25, 1995, at 1640 eastern standard time, a Beech 1900C, N34010, operated as Flight 2123 by GP Express Airlines, was struck by a moving tug while parked on the ramp at the Greater Cincinnati Airport, Covington, Kentucky. There were no injuries to the occupants, and the airplane received substantial damage. One ground handler received serious injuries. Visual meteorological conditions prevailed, and Flight 2123 had operated on an instrument flight plan under 14 CFR Part 135. According to interviews, after the airplane arrived at the gate area, the nose wheel was chocked. The forward cabin door was opened by the first officer, and the passengers remained seated, while the gate checked baggage was unloaded and placed next to the passenger exit. A tug with one baggage cart was parked on the left side of the airplane, pointed in the opposite direction of the airplane. After a few minutes, the unattended tug started to move under its own power. It completed a 270 degree turn to the right and struck the airplane on the nose landing gear, wrinkling the right side of the forward fuselage. The nose of the airplane was rotated approximately 90 degrees to the right. One baggage handler, who was unloading baggage from the aft baggage compartment, was struck by the airplane as the tail section rotated to the left, and fell to the ramp. She received a fractured elbow. Ground services for GP Express at Cincinnati, were handled by Continental Express. According to interviews and statements received from Continental Express, the company procedure was to set the parking brake when the tug was parked. The Station Manager reported that when he interviewed the tug driver after the occurrence, she did not remember if she had set the parking brake. When interviewed by the police, she reported that she had set the parking brake and placed the transmission in neutral. The Station Manager reported that the parking brake was found in the released position, and the tension on the parking brake handle was looser than normal. He was unable to determine if the brake had released on its own, due to vibration from the tug's engine, or had not been set. A chock was not used, or required to be used. There was no requirement to shut the engine off, if the tug was unoccupied.