On June 24, 2003, about 1510 eastern daylight time, an Embraer EMB-135-KL, N839AE, operating as American Eagle flight 4644, was substantially damaged during pushback from the ramp at Boston Logan International Airport (BOS), Boston, Massachusetts. There were no injuries to the 3-person crew, 31 passengers, or 2 tug operators. Visual meteorological conditions prevailed and an instrument flight rules flight plan was filed for the flight which was destined for Bangor International Airport (BGR), Bangor, Maine. The scheduled passenger flight was to be conducted under 14 CFR Part 121. According to representatives of American Eagle, as the airplane was being pushed back from the gate by a "Lektro" tug, the tug began to jackknife and the nose of the airplane came to rest 135 degrees from the heading of the tug. The tug operator could no longer push the airplane, and the wing walker who had been supervising him took over. He put the tug into reverse; however, he failed to straighten the steering wheel. As he moved the accelerator handle, the tug reversed directly into and underneath the airplane, impacting the fuselage. Examination of the airplane by a Federal Aviation Administration inspector revealed damage to the nose gear and a puncture to the underside of the fuselage, in the pressure vessel area. No mechanical deficiencies were noted with the tug.