On June 28, 2008, about 1815 eastern daylight time, a Bombardier Inc. CL-600-2C10 (CRJ 700), N725PS, was being pushed back for taxi to takeoff, when it struck a standing Bombardier Inc. CL-600-2B19 (CRJ 200), N228PS, at the Charlotte-Douglas International Airport (CLT), Charlotte, North Carolina. Both airplanes were substantially damaged, and both flights were operated by PSA Airlines Inc., doing business as US Airways Express. There were no injuries to the 2 flight crewmembers, 2 flight attendants, and 60 passengers on board the CRJ 700, or the 2 flight crewmembers, 1 flight attendant, and 45 passengers on board the CRJ 200. Visual meteorological conditions prevailed, and instrument flight rules flight plans were filed for both flights, which were conducted under the provisions of 14 Code of Federal Regulations (CFR) Part 121. According to a representative from PSA Airlines Inc., due to lightning in the vicinity of CLT, ground crew members were not utilizing headsets. The CRJ 200 had completed the pushback process from gate E21, and was waiting for taxi clearance. The CRJ 700 was parked at gate E12, when it was cleared for pushback by ramp control. A wing walker was stationed at the left wing, in plain sight of the tug driver. The wing walker was aware of the CRJ 200, and when the pushback commenced, he believed that the tug driver was only going to pushback the airplane about 10 feet, just enough to trigger the aircraft communication addressing and reporting system (ACARS) "out" time. As the tug driver continued to push the airplane past 10 feet, the wing walker signaled the tug driver to stop. He continued to attempt to alert the tug driver; however, the tug driver did not observe the wing walker before the tail section of the CRJ 700, struck the tail section of the CRJ 200. The empennages of both airplanes were substantially damaged. Two other ground crew members stated that they observed the wing walker signaling the tug driver to stop as the tug driver continued to push the airplane. One of the ground crew members, who was working at gate E14 ran toward the tug driver and tried to get his attention. He stated that the tug driver was focused on the cockpit of the airplane and was directing the starting of the airplane's number 2 engine. The tug driver stated that he began the pushback as normal and gave the flight crew the signal to start the number two engine. He was not aware that anything was wrong until he observed the ground crew member from gate E14.