NORAD officials have maintained consistently that had the passengers not caused United 93 to crash, the military would have prevented it from reaching Washington, D.C.
( ( NORAD ( officials ( have ( ( maintained consistently ) ( that ( ( ( had ( the passengers ) ) not ) ( ( caused ( ( United 93 ) ( to crash ) ) ) ( , ( ( ( the military ) ( would ( have ( ( prevented it ) ( from ( reaching Washington ) ) ) ) ) ) , ) ) ) ) ) ) ) ) ) D.C. )
(ROOT (SINV (VP (VBD NORAD) (SBAR (S (NP (NNS officials)) (VP (VBP have) (VP (VBN maintained) (ADVP (RB consistently)) (SBAR (IN that) (SINV (VBD had) (NP (DT the) (NNS passengers)) (RB not) (VP (VBN caused) (NP (NP (NNP United) (CD 93)) (PP (TO to) (NP (NN crash)))) (PRN (, ,) (S (NP (DT the) (NN military)) (VP (MD would) (VP (VB have) (VP (VBN prevented) (NP (PRP it)) (PP (IN from) (S (VP (VBG reaching) (NP (NNP Washington))))))))) (, ,)))))))))) (NP (NNP D.C.))))
NORAD officials have maintained that military would not have shot it down if the passengers hadn't crashed it, instead letting it travel until it ran out of fuel.
( ( NORAD officials ) ( ( have ( maintained ( that ( military ( ( would not ) ( have ( ( ( shot it ) down ) ( if ( ( the passengers ) ( ( had n't ) ( ( ( crashed it ) , ) ( instead ( letting ( it ( travel ( until ( it ( ( ran out ) ( of fuel ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP NORAD) (NNS officials)) (VP (VBP have) (VP (VBN maintained) (SBAR (IN that) (S (NP (JJ military)) (VP (MD would) (RB not) (VP (VB have) (VP (VBN shot) (NP (PRP it)) (ADVP (RB down)) (SBAR (IN if) (S (NP (DT the) (NNS passengers)) (VP (VBD had) (RB n't) (VP (VBN crashed) (NP (PRP it)) (, ,) (S (ADVP (RB instead)) (VP (VBG letting) (S (NP (PRP it)) (VP (VB travel) (SBAR (IN until) (S (NP (PRP it)) (VP (VBD ran) (PRT (RP out)) (PP (IN of) (NP (NN fuel))))))))))))))))))))) (. .)))