Aer Caribe flight JK1156, a Boeing 737-300 cargo plane sustained damage to the fuselage in a towing incident during pushback at Juan Santamaria Airport in Costa Rica. The tug driver was slightly injured. Probable Cause During a commercial flight, after the backward towing maneuver and during the forward towing maneuver to the “foxtrot” (F) position for release, the aircraft made an uncommanded turn to the right and impacted the towing truck with its right side of the fuselage, which caused considerable damage to the aircraft. It is presumed that this accident was due to: – The breakage of the fusible bolts of the tow bar, due to tangential stresses on these, which were the root cause that allowed the aircraft to continue with a divergent displacement trajectory and overtake the tractor trailer on its left. – Once the aircraft overtook the tractor trailer and continued to be hooked to it, the bar caused the nose wheel of the aircraft to turn to the right at an angle greater than 135 degrees, which caused it to make an uncontrolled turn of approximately 260ø to the right and impact the tow vehicle. Contributing factors directly related to the accident – Increased ground speed of the aircraft caused by both engines running, probable increase in speed of the tractor trailer and a 1.5% slope of the apron to the southwest. – Maneuver performed to center the aircraft on the taxi axis line.