A Lockheed L-1011, N724DA, operating Delta Air Lines flight DL189, experienced a collision with a Shorts 360, N376MQ, during pushback at the San Juan-Luis Munoz Marin International Airport, Puerto Rico. The Shorts operated American Eagle flight 5539. Visual meteorological conditions were favorable. The Delta Airlines airplane sustained minor damage, and the American Eagle airplane sustained substantial damage. There were no injuries. American Eagle flight 539 had requested and received permission to taxi from runway 10 to the ramp at 13:00:12. At 13:00:40, Delta Airlines flight 189 requested pushback clearance from ground control, and was approved at 13:00:43. The lead left wingman for Delta flight 189 stated they had just commenced pushback from gate 33 when he observed an American Eagle flight taxiing behind flight 189. He signaled the tug operator to stop the pushback. The American Eagle flight taxied past flight 189, stopped, started taxiing again, and stopped abruptly. The tug operator commenced pushback procedures without receiving instructions from the dispatching agent. The wingman signaled the tug operator to stop, however; the right wing tip of Delta flight 189 collided with the rudder of American Eagle flight 5539 before the pushback was stopped. Delta Airlines SOP states, the dispatching ramp agent is responsible for directing the movement of aircraft. It also states the dispatching ramp agent is responsible for observing obstruction clearance and executing the appropriate ramp signals to the tug operator. It further states the tug operator is responsible for following the signals of the dispatching ramp agent. PROBABLE CAUSE: ‘The failure of the tug operator to follow correct pushback procedures by commencing pushback without clearance, resulting in an on-ground collision with another airplane.’A Lockheed L-1011, N724DA, operating Delta Air Lines flight DL189, experienced a collision with a Shorts 360, N376MQ, during pushback at the San Juan-Luis Munoz Marin International Airport, Puerto Rico. The Shorts operated American Eagle flight 5539. Visual meteorological conditions were favorable. The Delta Airlines airplane sustained minor damage, and the American Eagle airplane sustained substantial damage. There were no injuries. American Eagle flight 539 had requested and received permission to taxi from runway 10 to the ramp at 13:00:12. At 13:00:40, Delta Airlines flight 189 requested pushback clearance from ground control, and was approved at 13:00:43. The lead left wingman for Delta flight 189 stated they had just commenced pushback from gate 33 when he observed an American Eagle flight taxiing behind flight 189. He signaled the tug operator to stop the pushback. The American Eagle flight taxied past flight 189, stopped, started taxiing again, and stopped abruptly. The tug operator commenced pushback procedures without receiving instructions from the dispatching agent. The wingman signaled the tug operator to stop, however; the right wing tip of Delta flight 189 collided with the rudder of American Eagle flight 5539 before the pushback was stopped. Delta Airlines SOP states, the dispatching ramp agent is responsible for directing the movement of aircraft. It also states the dispatching ramp agent is responsible for observing obstruction clearance and executing the appropriate ramp signals to the tug operator. It further states the tug operator is responsible for following the signals of the dispatching ramp agent. PROBABLE CAUSE: ‘The failure of the tug operator to follow correct pushback procedures by commencing pushback without clearance, resulting in an on-ground collision with another airplane.’