Navistar is recalling certain model year 2013-2014 IC Bus AE, and 2011-2014 BE, CE, and RE buses. These buses were manufactured February 11, 2010, through June 17, 2013. The passenger seat foam padding did not adequately reduce the impact forces to the knee in the lower outside corners of the seat back during compliance testing. Thus, these buses fail to conform to the requirements of Federal Motor Vehicle Safety Standard (FMVSS) No. 222, “School Bus Passenger Seating and Crash Protection.”