NTSB Factual Report

On August 14, 2014, about 0941 mountain daylight time, a Boeing 737-700 airplane, N758SW, was struck by a runaway baggage cart while sitting at the boarding gate, at the Salt Lake City International Airport (KSLC), Salt Lake City, Utah. The two airline transport pilots and three cabin crewmembers were not injured. The fuselage was substantially damaged. The airplane was registered to, and operated by, the Southwest Airlines Company, Dallas, Texas, as Southwest Flight 579, as a Title 14 Code of Federal Regulations Part 121 domestic passenger flight. An instrument flight rules flight plan was filed. The airplane was being prepared to board passengers when the event occurred.

During a telephone conversation with the National Transportation Safety Board (NTSB) investigator-in-charge (IIC) on August 14, a representative of the Southwest Airlines Company said that he had been advised of the event in Salt Lake City, and received photographs showing structural damage to the airplane. He said the baggage cart had been on the end of a string of carts being pulled by a tug belonging to Delta Airlines. The cart came loose while being towed and rolled into the airplane, penetrating the side of the fuselage.

During a subsequent telephone conversation, a representative of Delta Airlines reported that a tug, belonging to Delta Airlines, had been pulling several baggage carts in the non-movement area adjacent to the airplane boarding gates. She said an airport surveillance video showed the second cart in the string hit a pothole and detached from the preceding cart. The loose baggage carts rolled across the ramp and into the side of the airplane.

Prior to the accident, there were no reported mechanical anomalies with the airplane.

According to a Salt Lake City Airport Police report, the Delta Employee who drove the event tug stated he was pulling a string of four baggage carts behind his tug, northbound on the airfield road on the east side of the Bravo Concourse. He said he was coming from Gate B-3 heading north to the baggage cart boneyard. He further reported that when he arrived at the boneyard, there was only 1 baggage cart attached to the tug. He did not know when or where the 3 missing carts had detached from the string.

A Southwest employee reported to the police that he was pulled up to the rear-belt loader on gate B-17. He detached 2 baggage carts from his tug and got back in his tug. He looked up and saw 3 Delta baggage carts rolling towards the belt-loader. He yelled to his fellow-employee to watch out, and the baggage carts swerved at the last second and collided with the airplane.

The second Southwest employee reported that he was standing by the belt-loader with his back to the airplane when he heard someone scream, "Lookout!!" He turned around just as the carts impacted the airplane. He reported that the carts impacted the airplane so hard the rear carts spun around.

The police report went on to report that security video recordings were obtained and showed that in the areas of Gates B-13 and B-15, the Delta Employee could be seen driving the tug out of his traffic lane veering to his left into the south bound traffic lane. The Employee reported that, that was done to avoid an airplane taxiing away from Gate B-15.

The report continued that, while traveling north in the southbound lane, the Delta Employee drove over a drain cover east of Gate B-15. When the baggage carts passed over the drain cover, the second baggage cart disconnected from the first baggage cart.

According to a Delta representative, after being notified of the event, Delta inspected the tug and baggage carts involved. They reported that all connection parts (tongues and springs) were found to be in good condition. Delta also reported that an additional video showed the tug maneuvering in a gate area for an extended period of time with the same carts attached. Delta reported that the tug driver stated he was confident the carts were properly connected.

Previous Events

During the airlines' investigations, employees at both Southwest and Delta reported knowing about the dip in the driving lane at the drain cover near Gate B15. Employees stated other similar disconnection events had occurred, but since the events did not result in damage or injury, documentation could not be located or did not exist.

The Southwest station manager reported that in November of 2013 an event occurred at the same spot in which a baggage cart disconnected from a tug. He stated the event was brought to the attention of airport authorities who stated the surface could not be leveled at that time because of the winter weather. The Station Manager further stated no action has been taken by the airport since that time.

NTSB Probable Cause

The disconnection of baggage carts that subsequently collided with the parked airplane following the tug driving over a dip in the roadway.