What happened
The FAA’s narrative, in sentence case. The FAA writes it in capitals and removes private details.
privacy data omitted Aircraft N11189 was parked on gate A2E at 07:30 by the privacy data omitted tow team. Aircraft N11189 is an ERJ145. The aircraft was mistakenly parked on the ERJ135 stop bar; this resulted in the left winglet of the aircraft protruding approximately 4? Into the taxiway and outside of the operational safety zone (osz). Investigation revealed that the marshaller was on the incorrect side of aircraft (right side) and did not have line of sight to stop bar labels. Two employees performed post move walk arounds and failed to notice incorrect stop bar as well as the left-hand winglet hanging over the osz.
privacy data omitted Aircraft N11150 arrived at Washington Dulles international airport (iad) at 09:57 and was parked at gate stand A4A. The aircraft was offloaded and loaded without incident and cleared to depart gate A4A at 10:50. The pilot made contact with the pushback operator and asked him to hold on the push as a privacy data omitted 767 aircraft was taxiing immediately behind the gate A4. The pushback operator asked the captain if he could push the aircraft to the middle of the gate stand taxilane so they could push straight back after the 767 passed. The pilot agreed to this and the pushback of ua flight 4937 began. The pushback was delayed for a few seconds to allow for an abm vehicle on the left side of the aircraft to make a 5 point turn and exit the gate stand. After the pushback began, an mwaa maintenance truck turned into the gate area from the vsr near the center of the taxilane. The mwaa vehicle looped around the left side of the abm vehicle then turned left into the area between A4A and A4B.
The pushback operator noticed both vehicles to his right and over compensated his pushback to the left side of the center line. Aircraft N11150 was still inside the taxilane, but left of the center line. The wingwalker on the right side of the aircraft noticed the overhang of aircraft N11189?s wing in the taxilane and signaled an ?x? To the left side wingwalker. The left side wingwalker relayed the ?x? Signal to the pushback operator. The pushback operator was unable to stop aircraft N11150 before the back of its right winglet made contact with the front of aircraft N11189?s left winglet.
After the contact of the winglets, the captain of aircraft N11150 requested that the aircraft be pulled back into gate stand A4A.
As the FAA filed it
^PRIVACY DATA OMITTED^ AIRCRAFT N11189 WAS PARKED ON GATE A2E AT 07:30 BY THE ^PRIVACY DATA OMITTED^ TOW TEAM. AIRCRAFT N11189 IS AN ERJ145. THE AIRCRAFT WAS MISTAKENLY PARKED ON THE ERJ135 STOP BAR; THIS RESULTED IN THE LEFT WINGLET OF THE AIRCRAFT PROTRUDING APPROXIMATELY 4? INTO THE TAXIWAY AND OUTSIDE OF THE OPERATIONAL SAFETY ZONE (OSZ). INVESTIGATION REVEALED THAT THE MARSHALLER WAS ON THE INCORRECT SIDE OF AIRCRAFT (RIGHT SIDE) AND DID NOT HAVE LINE OF SIGHT TO STOP BAR LABELS. TWO EMPLOYEES PERFORMED POST MOVE WALK AROUNDS AND FAILED TO NOTICE INCORRECT STOP BAR AS WELL AS THE LEFT-HAND WINGLET HANGING OVER THE OSZ.
^PRIVACY DATA OMITTED^ AIRCRAFT N11150 ARRIVED AT WASHINGTON DULLES INTERNATIONAL AIRPORT (IAD) AT 09:57 AND WAS PARKED AT GATE STAND A4A. THE AIRCRAFT WAS OFFLOADED AND LOADED WITHOUT INCIDENT AND CLEARED TO DEPART GATE A4A AT 10:50. THE PILOT MADE CONTACT WITH THE PUSHBACK OPERATOR AND ASKED HIM TO HOLD ON THE PUSH AS A ^PRIVACY DATA OMITTED^ 767 AIRCRAFT WAS TAXIING IMMEDIATELY BEHIND THE GATE A4. THE PUSHBACK OPERATOR ASKED THE CAPTAIN IF HE COULD PUSH THE AIRCRAFT TO THE MIDDLE OF THE GATE STAND TAXILANE SO THEY COULD PUSH STRAIGHT BACK AFTER THE 767 PASSED. THE PILOT AGREED TO THIS AND THE PUSHBACK OF UA FLIGHT 4937 BEGAN. THE PUSHBACK WAS DELAYED FOR A FEW SECONDS TO ALLOW FOR AN ABM VEHICLE ON THE LEFT SIDE OF THE AIRCRAFT TO MAKE A 5 POINT TURN AND EXIT THE GATE STAND. AFTER THE PUSHBACK BEGAN, AN MWAA MAINTENANCE TRUCK TURNED INTO THE GATE AREA FROM THE VSR NEAR THE CENTER OF THE TAXILANE. THE MWAA VEHICLE LOOPED AROUND THE LEFT SIDE OF THE ABM VEHICLE THEN TURNED LEFT INTO THE AREA BETWEEN A4A AND A4B.
THE PUSHBACK OPERATOR NOTICED BOTH VEHICLES TO HIS RIGHT AND OVER COMPENSATED HIS PUSHBACK TO THE LEFT SIDE OF THE CENTER LINE. AIRCRAFT N11150 WAS STILL INSIDE THE TAXILANE, BUT LEFT OF THE CENTER LINE. THE WINGWALKER ON THE RIGHT SIDE OF THE AIRCRAFT NOTICED THE OVERHANG OF AIRCRAFT N11189?S WING IN THE TAXILANE AND SIGNALED AN ?X? TO THE LEFT SIDE WINGWALKER. THE LEFT SIDE WINGWALKER RELAYED THE ?X? SIGNAL TO THE PUSHBACK OPERATOR. THE PUSHBACK OPERATOR WAS UNABLE TO STOP AIRCRAFT N11150 BEFORE THE BACK OF ITS RIGHT WINGLET MADE CONTACT WITH THE FRONT OF AIRCRAFT N11189?S LEFT WINGLET.
AFTER THE CONTACT OF THE WINGLETS, THE CAPTAIN OF AIRCRAFT N11150 REQUESTED THAT THE AIRCRAFT BE PULLED BACK INTO GATE STAND A4A.