On February 1, 2004, at 1700 eastern standard time, a Saab 340A, N158SD, operated by Shuttle America Inc., as US Airways Express flight 4593, was substantially damaged when it was struck by a baggage cart while parked at Gate E11 at Pittsburgh International Airport (PIT), Pittsburgh, Pennsylvania. The two flightcrew members, one flight attendant, and 19 passengers were not injured. Visual meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the flight which was destined for Toledo International Airport (TOL), Toledo, Ohio. The scheduled passenger flight was to be conducted under 14 CFR Part 121. According to the operator, the airplane was parked at the gate, when a baggage cart became disconnected from the tug which was towing it, and impacted the left side of the fuselage. Substantial damage to the airplane included a 23-inch tear in the fuselage, as well as five circumferential structure fractures. Examination of the tug revealed a broken E-hitch pin where the baggage cart became disconnected. Ground service personnel then examined all tugs and their associated baggage carts to identify any additional faulty gearshift levers. During the inspection, one additional tug was identified as having a broken pin. The pin was replaced, and the vehicle was returned to service.