Date: 202103
Local time of day: 0001-0600
Location: ZZZ.Airport, US
Flight conditions: VMC
Light: Night
Aircraft: B737-800
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Taxi
Aircraft component: Wing
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Pilot Not Flying; First Officer
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Human factors: Communication Breakdown
Second reporter function: Pilot Flying; Captain
Anomaly: Aircraft Equipment Problem Less Severe; Conflict Ground Conflict; Critical; Deviation / Discrepancy - Procedural Published Material / Policy; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural FAR; Ground Event / Encounter Vehicle; Ground Event / Encounter Ground Equipment Issue
Detector: Person Ground Personnel
When detected: Other pushback
Result: Aircraft Aircraft Damaged; Flight Crew Returned To Gate; General Maintenance Action
Contributing factors: Environment - Non Weather Related; Human Factors; Procedure
Primary problem: Human Factors

Narrative: Pushback was delayed due to catering (and vehicles impeding the catering truck from approaching the aircraft).  Following push clearance; the tug began the push but we came to a stop after approx. 15 sec. I thought perhaps something crossed behind us and we would resume the push.  But; after a few more seconds; the tug driver said that a catering truck wasn't moving.  That seemed odd; and the Captain and I wondered why a catering truck wouldn't clear a moving aircraft.  That's when the Captain looked through his side window; over his shoulder and told me; 'THAT'S why the truck isn't moving - it's sitting under our wingtip!' We hadn't felt anything and the tug driver was asked if we were touching.  He said that he couldn't tell.  A crowd gathered.  I informed ramp of our situation and our intent to remain in position to investigate. A maintenance rep came on interphone and let us know it was difficult to determine how close the wingtip was to the roof of the truck.  It was judged safe to set brakes. After some time; it was decided to let air out of the truck's tires.  Personnel climbed atop the truck and after getting a closer look; the truck was moved.  No visible contact/damage was noted but the possibility was mentioned that the winds were moving the aircraft slightly and the wingtip may have bounced off the roof and that may have not been enough to show damage but that an inspection would be the best course of action.  We were cleared to be pulled forward to the gate and the aircraft was taken out of service and the crew and passengers deplaned to the aircraft at the adjoining gate.  The remainder of the flight was uneventful.Since we were being pushed straight back; we did not see the events leading up to the potential contact.  It would seem that a combination of catering truck driver and wing walker inattention may have contributed.[Suggest] Company communications to [the catering company] and maintenance re-iterating the need to be vigilant.


Second narrative: About 60 feet into a routine pushback; the aircraft stopped.  The Tow Driver told us a 'catering truck driver is refusing to move.'  I asked if I should set the Parking Brake.  The Tow Driver said 'No.'  I looked out the left window and saw a catering truck with no driver in the cab.  I called Ramp Control on the radio to report the situation.     I looked out the window again to see a Maintenance Technician on the catering truck's over-the-cab loading platform.  He was leaning on the railing to look toward the aft-right side of the truck.  I opened the aircraft L2 Window to get a better view.  I saw the Left Wing apparently resting on the middle; top-right of the back portion of the catering truck.  I saw numerous Ground Crew and Maintenance personnel walking around the catering truck gesturing at the apparent contact point.     A Maintenance Supervisor saw me looking out the window and got on the Ground Interphone to tell me what was going on.  She said they thought there was actually no contact with the catering truck but couldn't be sure until they employed an operable hydraulic work lift - the first one they tried was inoperative.  I asked how big/small the gap was.  She thought the wing was about an inch from touching the truck; but the wind was causing the aircraft to gently rock; possibly bouncing the wing off the top of the truck.     After many minutes; a plan emerged to deflate the tires of the catering truck and tow it out of the way; preventing any possible further contact with the wing as the wind blew.  After the catering truck was clear; the Maintenance Supervisor got back on the Ground Interphone to tell us the aircraft was being taken out of service as a precaution and a replacement Ground Crew would tow us back to the gate for deplaning.  We were not to set the parking brake until safely at the gate.  Company Operations and Maintenance coordinated a different aircraft for us to continue the flight.     The tow was uneventful.  Once parked; we ran the Shutdown Checklist.  Maintenance Technicians boarded and asked us to not shut down the aircraft.  They also invited the First Officer and me to go outside and get on the work lift to inspect the wing.  To my eye; there was absolutely no indication of any kind that the wing had contacted the catering truck; however; I know that painted panels of modern materials can deform; return to shape; and not show outward signs of damage.  Not that it was my decision; but I concurred with Maintenance in taking the aircraft out of service.     Passengers and crew boarded the new aircraft and departed uneventfully.Cause Unknown.  I would only be speculating on events that occurred out of my view.I can only speculate how this event occurred; so I cannot provide prevention suggestions.


Synopsis: Flight Crew reported a gate return due to possible aircraft damage from a possible collision with a catering truck during push back.