Transponder .doc from www.icasc.co
Three of the four reportedly hijacked September 11 flights also stopped providing secondary radar data to ATC via Mode S transponders during their flights. These Mode S transponder data losses were officially attributed to manual deactivations by alleged hijackers, although evidence to confirm this claim was never cited by the 9/11 Commission Report. September 11 flight transponder data losses contributed significantly to a circumstantial impression of alleged hijacker flight deck takeovers and also coincided with significant nationwide US military exercises that day.