On March 12, 1995, about 1305 Atlantic standard time, a Lockheed L-1011, N724DA, flight number 189, experienced an on-ground collision during pushback at the Luis Munoz Marin International Airport, San Juan, Puerto Rico, with a Short SD3-60, N376MQ. The L-1011 is registered to Delta Airlines Inc., operating as a 14 CFR Part 121 scheduled domestic passenger flight. The Short SD3-60, is registered to Security Pacific esquire, operating as a 14 CFR Part 121 scheduled domestic passenger flight, by Executive Airlines Inc., doing business as American Eagle flight 5539. Visual meteorological conditions prevailed and an IFR flight plan was filed for both airplanes. The Delta Airlines airplane sustained minor damage and the American Eagle airplane sustained substantial damage. The Delta Airlines airline transport pilot-in-command, airline transport pilot first officer, flight engineer, 8 flight attendants, and 302 passengers were not injured. The American Eagle airline transport pilot-in-command, commercial pilot first officer, 1 flight attendant and 23 passengers were not injured. The Delta Airlines flight was originating at San Juan, Puerto Rico, and the American Eagle flight originated from St. Thomas, U.S. Virgin Islands, about 31 minutes before the accident. The lead left wingman, for Delta Airlines 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. Review of ATC transcripts from the time period of 1255:00 to 1308:00 revealed American eagle flight 539 requested and received permission to taxi from runway 10 to the ramp at 1300:12. At 1300:40, Delta Airlines flight 189 requested pushback clearance from ground control, and was approved at 1300:43. American Eagle flight 539 advised ground control "that delta aircraft just hit us on our tail pushing back." Delta flight 189 requested and received permission from ground control to return to the departure gate at 1303:37. The tug operator was interviewed by the FAA on March 12, 1995. The tug operator stated upon receiving initial clearance he began pushback operations, and stopped the pushback when he observed an American Eagle SD3-60 taxiing behind the aircraft from east to west. When he observed the SD3-60 on the west side of the L-1011, he resumed pushback operations, without receiving clearance from the dispatching agent. 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.