The duty officer replied that security personnel at headquarters had just begun discussing the apparent hijack on a conference call with the New England regional office.
( ( The ( duty officer ) ) ( ( replied ( that ( ( ( security personnel ) ( at headquarters ) ) ( ( had just ) ( begun ( ( discussing ( the ( apparent hijack ) ) ) ( on ( ( a ( conference call ) ) ( with ( the ( New ( England ( regional office ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NN duty) (NN officer)) (VP (VBD replied) (SBAR (IN that) (S (NP (NP (NN security) (NNS personnel)) (PP (IN at) (NP (NN headquarters)))) (VP (VBD had) (ADVP (RB just)) (VP (VBN begun) (S (VP (VBG discussing) (NP (DT the) (JJ apparent) (NN hijack)) (PP (IN on) (NP (NP (DT a) (NN conference) (NN call)) (PP (IN with) (NP (DT the) (NNP New) (NNP England) (JJ regional) (NN office)))))))))))) (. .)))
There have been dozens of plane hijackings before 9/11.
( There ( ( have ( ( been ( dozens ( of ( plane hijackings ) ) ) ) ( before 9/11 ) ) ) . ) )
(ROOT (S (NP (EX There)) (VP (VBP have) (VP (VBN been) (NP (NP (NNS dozens)) (PP (IN of) (NP (NN plane) (NNS hijackings)))) (PP (IN before) (NP (CD 9/11))))) (. .)))