The National Transportation Safety Board is investigating a runway incursion Sept. 19 at Allentown, PA involving a Cessna 172 (N736GV) and a Chicago-bound CRJ-700 (N506MJ) operated by Mesa Airlines. The Cessna was on a landing roll on Runway 6 at Lehigh Valley International when the pilot was instructed to exit the runway at Taxiway A4. Mesa Flight 7138, already instructed to position and hold on the same runway, was then given clearance by the same controller to take off. During the takeoff roll, the Mesa crew heard the Cessna pilot say that he'd missed the Taxiway A4 turnoff and ask to exit at Taxiway B. The Mesa crew saw the Cessna ahead on the runway and aborted the takeoff at about 120 knots, swerving around the Cessna. The Mesa crew estimated that they missed colliding with the Cessna by about 10 feet. There were no injuries on either aircraft.