An Airbus A320, registered VH-VGR and operated by Jetstar Airways, operated on a domestic flight from Sydney, Australia to Melbourne. Upon arrival, the flight was cleared by the ground controller to taxi to gate D2. At 09:30 the aircraft entered the apron en route to gate D2, when a Boeing 737-800, registered VH-YID, requested pushback approval from gate E1. The 737 was being operated by Virgin Australia Airlines on a flight to Sunshine Coast Airport. The controller advised the crew of that a Jetstar A320 was entering the apron behind them for bay D2 and that when that traffic was ‘on the gate’, pushback from bay E1 was approved. The flight crew of VH-YID reported that they saw the Jetstar A320 pass behind them from the reflection in the terminal window in front of their parked aircraft. The captain of VH-YID relayed the pushback approval to the dispatcher, including that it could only commence once the A320 was on the gate. The dispatcher was standing to the right of the aircraft’s nose. At 09:31:34, as VH-VGR approached the gate on bay D2, the automatic nose-in guidance system (NIGS) displayed a message ‘STOP-WAIT’. In response the flight crew stopped the aircraft short of the gate. The dispatcher on VH-YID reported looking under the aircraft and observing that the A320 was stopped. The dispatcher reported then waiting for about 15–20 seconds to confirm the aircraft remained stationary. As it did, the dispatcher was satisfied that the A320 was on the gate and the pushback of VH-YID could commence. Pushback began at 09:31:46. At 09:31:58, the crew of the A320 transmitted to the controller that they were holding short of the bay because of the NIGS. However, that message was over-transmitted by another aircraft. Forty seconds later, the crew re-transmitted the same message. The message was acknowledged by the controller, who requested to be advised when the aircraft was at the gate. Neither the crew of VH-VGR nor the controller mentioned the gate number during the transmissions. The crew of the 737 later reported they did not hear these transmissions. At 09:33:03, the left wingtip of VH-YID contacted the tail cone of the A320 immediately aft of the operating auxiliary power unit. The tail cone immediately aft of the auxiliary power unit separated from the aircraft and fell to the ground. The left wingtip of VH-YID was damaged during the collision. Following the collision, VH-YID was towed back to gate E1 and VGR was marshalled to gate D2.There were no injuries as a result of the collision. Contributing factors: – The dispatcher of the B737 could not visually confirm the position of the A320 relative to its assigned gate and incorrectly assessed that, as the aircraft was stationary, it was at the gate. – The pushback of the B737 was commenced with insufficient clearance from the A320, which was not identified prior to the collision as the dispatcher’s position to the right-front of the B737 prevented observation of its left wing.