On January 6, 1998, at 1210 eastern standard time, American Airlines Flight 2027, a Boeing 727-223, N845AA, sustained minor damage when it was struck by a ground tug while taxiing for takeoff at the Philadelphia International Airport, Philadelphia, Pennsylvania. The certificated airline transport captain, first officer, flight engineer, 4 flight attendants, and 107 passengers were not injured. The driver of the tug received serious injuries. Instrument meteorological conditions existed and a instrument flight plan was filed. The scheduled domestic flight was conducted under 14 CFR Part 121, destined for Dallas/Fort Worth, Texas. The pilot stated that after push back from the gate, they were taxiing to spot number 2 in the "non movement" area, when they felt an impact. The captain stated he thought the airplane had experienced a blown tire and neither he nor any of the cockpit crew saw the tug prior to impact. The Cockpit Voice Recorder was removed from the airplane and verified the pilot's statement. Federal Aviation Administration (FAA) Inspectors gathered witness statements, which indicated that the tug, pulling baggage carts, did not attempt to slow up or avoid the airplane. The FAA Inspectors stated that there were no skid marks left by the tug prior to the collision. When the airplane came to a stop, the tug was under the airplane's right main wheel mount, and one of the baggage carts being towed was impacted by the left main wheel mount. The damage to the airplane was confined to the leading edge of the left wing root and to the bottom of the fuselage. The tug was found at the scene with the engine running and the transmission engaged. The FAA Inspectors, with assistance from the Philadelphia police, examined the tug and reviewed the "Work History" and "Direct Labor and Parts" forms for the tug. No pertinent problems were written on the forms, and the vehicle's brakes and steering were found in good operating condition. The driver's training record was reviewed and current, with his last physical completed October 14, 1997. The driver was on vacation from December 23, 1997, through January 5, 1998. After a 2 week vacation, this was the tug driver's first day back at work. He had been operating this tug since 0430, without any reported mechanical problems. The emergency room doctor stated that the tug driver had lost 11 pints of blood from the injuries sustained in the accident. No symptoms of any medical events which would have caused the driver to lose consciousness were discovered. Tests results for drugs and alcohol were negative. Two nights after the accident while recovering from his injuries, the tug driver called his supervisor and relayed, "that while driving the tug, he had dropped his water container, and was reaching down for it. That was the last thing that he could remember." An assessment team from American Airlines, along with FAA Inspectors from the Philadelphia Flight Standards District Office, documented the damage sustained by the airplane. On January 8, 1998, the airplane was released to American Airlines and on January 12, 1998, after an examination of the damaged tug and its maintenance logbook, the tug was released.