On August 4, 2015, about 1800 mountain daylight time, a Boeing 737-700 airplane, N779SW, sustained minor damage when it collided with a provisioning truck at Denver International Airport (DEN), Denver, Colorado. The flight crew and passengers on board the airplane were not injured. The driver in the service truck sustained minor injuries. The aircraft was registered to and operated by Southwest Airlines under the provisions of 14 Code of Federal Regulations Part 121 as a scheduled domestic passenger flight. Visual meteorological conditions prevailed prior to and during the ground operations. The flight was originating at the time of the collision.The airplane was parked at Gate C28. A video of the event was provided to the investigator-in-charge by Southwest Airlines. The video started at a time stamp of 05:56:43 PM (MDT) on August 4, 2015. When the video started the provisioning truck was already parked on the far side of the airplane. The following is a timeline of the significant events captured by the video:

05:57:44 – Luggage belt pulls away from the right front side of the airplane 05:58:15 – The jet bridge starts to pull away from the airplane 05:58:36 – The gate lead appears to start his walk around 05:59:02 – The gate lead moves a safety cone from under the left wing and starts to walk towards the rear of the airplane (after this he is no longer visible to the camera) 05:59:29 – The gate lead is visible again under the empennage of the airplane 06:00:28 – The gate lead boards the airplane tug and the wing walker walks towards the right wing tip 06:00:53 – The Southwest Airlines (SWA) airplane scheduled for gate 26 arrives and starts to turn towards the gate 06:01:02 – The tug driver started to push the SWA airplane at gate 28 back as the SA airplane at gate 26 continued to pull in 06:01:17 – The collision between the airplane's left wing and the provisioning truck started 06:01:24 – The airplane stopped moving backwards and the truck stopped its roll

The outboard trailing edge of the left wing collided with the fiberglass box on the passenger's side of the provisioning truck. The provisioning truck rolled and came to rest on the driver's side of the truck. The pushback driver immediately stopped the operations and the driver of the provisioning truck egressed from the truck without further incident. The trailing edge of the wing sustained minor impact damage to the skin, 2 inches in width and 18 inches in length.

According to an interview with the lead agent/tug driver for gate 28, this was his first airplane of the day. He conducted a walk around the airplane but did not recall seeing the provisioning truck parked inside of the safety area. After understanding that he was cleared to push back by both the wing walker and the pilot, he started to push back. He stopped the push when he felt the tug or jerk of the airplane as it hit the provisioning truck. He commented that his headset was having issues. He also commented that he was stressed and potentially distracted by personal issues.

In an interview with the guide agent, he stated that he did see the provisioning truck but it was not clear to him that it was in the safety area for gate 28. He assumed that it was clear and no issue as the lead agent/tug driver had walked passed it during his walk around and had subsequently announced that the walk around was complete. He was on the opposite side of the airplane during the pushback and commented that a second wing walker would have prevented this from happening.

According to an interview with the provisions agent, he had parked outside of the safety area for gate 26 but acknowledged later that he was likely within the safety area for gate 28. He was awaiting an inbound airplane to service at gate 26. He also commented that he had never been told to remain clear of safety areas for adjacent gates, only to move his truck if he were asked. He did not receive such a request from the ground crew for gate 28.

The Ground Operations Manual – 5.19.2 Pushback Procedures and Radio Communications and the Prepush Checklist (WN-1095 – REV. 11/12) for the pushback driver included an observation for the driver to ensure that the safety zone was clear of FOD, personnel, and equipment. The Provisioning Manual – Safety Section – 10.5 Driving and Ramp Safety 2.6.7 (Parking of Provisioning Vehicles Between Safety Zones – stated "Employees holding short at the gate for incoming aircraft should always make sure they are outside the safety zone. In addition, they should be aware of incoming flights that are to arrive at the adjacent gate and of flights that are pushing from an adjacent gate."