Unlike Flight 11 , which turned Change its transponder off , the aircraft 's transponder was visible on New York Center 's radar , and the aircraft deviated Change from the assigned flight path for four minutes before air traffic controllers noticed Know these changes Change at 08:51 EDT .

Unlike Flight 11 , which turned Change its transponder off , the aircraft 's transponder was visible on New York Center 's radar , and the aircraft deviated Change from the assigned flight path for four minutes before air traffic controllers noticed Know these changes Change at 08:51 EDT .