Radar reconstructions performed after 9/11 reveal that FAA radar equipment tracked the flight from the moment its transponder was turned off at 8:56.
( ( ( Radar reconstructions ) ( performed ( after 9/11 ) ) ) ( ( reveal ( that ( ( FAA ( radar equipment ) ) ( ( tracked ( the flight ) ) ( from ( ( the moment ) ( ( its transponder ) ( was ( ( turned off ) ( at 8:56 ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (JJ Radar) (NNS reconstructions)) (VP (VBN performed) (PP (IN after) (NP (CD 9/11))))) (VP (VBP reveal) (SBAR (IN that) (S (NP (NNP FAA) (NN radar) (NN equipment)) (VP (VBD tracked) (NP (DT the) (NN flight)) (PP (IN from) (NP (NP (DT the) (NN moment)) (SBAR (S (NP (PRP$ its) (NN transponder)) (VP (VBD was) (VP (VBN turned) (PRT (RP off)) (PP (IN at) (NP (CD 8:56))))))))))))) (. .)))
There was no prior information about the airplane that caused 9/11.
( There ( ( was ( ( no ( prior information ) ) ( about ( ( the airplane ) ( that ( caused 9/11 ) ) ) ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBD was) (NP (NP (DT no) (JJ prior) (NN information)) (PP (IN about) (NP (NP (DT the) (NN airplane)) (SBAR (WHNP (WDT that)) (S (VP (VBD caused) (NP (CD 9/11))))))))) (. .)))