On October 11, 1998, about 1854 eastern standard time, a McDonnell Douglas MD-88, N997DL, operated by Delta Airlines as Flight 1726, sustained substantial damage when it was struck by a baggage tug while taxiing for takeoff at Cincinnati/Northern Kentucky International Airport (CVG), Covington, Kentucky. The 2 flight crewmembers, 5 flight attendants, 114 passengers, and the tug driver were not injured. Instrument meteorological conditions prevailed and an instrument flight rules flight plan had been filed for the scheduled passenger flight that was conducted under 14 CFR Part 121. In a written statement, the captain stated that the airplane was taxiing west abeam "B12" and "B10," when he and the first officer saw a "bag tug" approaching. The tug was between the "A" and "B" concourses moving at a fairly high rate of speed, with the driver looking away from the airplane. The captain added that the driver was unaware of the airplane. The captain and first officer then applied maximum braking and the airplane "was almost stopped" when the tug impacted the side of the airplane. According to a passenger, the airplane pushed back from the gate and started to taxi for the runway, when she saw a tug "quickly" approaching from the right. She could also see that the tug driver was looking to his right and nowhere else. She continued, "He never slowed down, never turned. He drove under the plane, right under us, full speed. I thought we crushed him. He reappeared, windows broken, metal superstructure of tug listing and drove rapidly away." The passenger added that, "I think he had earphones on. According to company records, the tug driver received a total of 30 hours of training in the month of August. The training covered, ramp and operation self directed training, dangerous goods handling, basic ramp procedures, and driver training. The tug driver's employment was terminated after the accident and he was not available for comment nor did he submit a statement.