On 9/11, the terrorists turned off the transponders on three of the four hijacked aircraft.
( ( On 9/11 ) ( , ( ( the terrorists ) ( ( ( ( turned off ) ( the transponders ) ) ( on ( three ( of ( the ( four ( hijacked aircraft ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN On) (NP (CD 9/11))) (, ,) (NP (DT the) (NNS terrorists)) (VP (VBD turned) (PRT (RP off)) (NP (DT the) (NNS transponders)) (PP (IN on) (NP (NP (CD three)) (PP (IN of) (NP (DT the) (CD four) (JJ hijacked) (NN aircraft)))))) (. .)))
None of the hijacked airplanes turned of their transponder.
( ( None ( of ( the ( hijacked airplanes ) ) ) ) ( ( turned ( of ( their transponder ) ) ) . ) )
(ROOT (S (NP (NP (NN None)) (PP (IN of) (NP (DT the) (JJ hijacked) (NNS airplanes)))) (VP (VBD turned) (PP (IN of) (NP (PRP$ their) (NN transponder)))) (. .)))