By 9:20, Indianapolis Center learned that there were other hijacked aircraft, and began to doubt its initial assumption that American 77 had crashed.
( ( By 9:20 ) ( , ( ( Indianapolis Center ) ( ( ( ( ( learned ( that ( there ( were ( other ( hijacked aircraft ) ) ) ) ) ) , ) and ) ( began ( to ( ( doubt ( its ( initial assumption ) ) ) ( that ( ( American 77 ) ( had crashed ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN By) (NP (CD 9:20))) (, ,) (NP (NNP Indianapolis) (NNP Center)) (VP (VP (VBD learned) (SBAR (IN that) (S (NP (EX there)) (VP (VBD were) (NP (JJ other) (JJ hijacked) (NN aircraft)))))) (, ,) (CC and) (VP (VBD began) (S (VP (TO to) (VP (VB doubt) (NP (PRP$ its) (JJ initial) (NN assumption)) (SBAR (IN that) (S (NP (NNP American) (CD 77)) (VP (VBD had) (VP (VBD crashed)))))))))) (. .)))
American 77 was confirmed to have crashed in an unrelated incident.
( ( American 77 ) ( ( was ( confirmed ( to ( have ( crashed ( in ( an ( unrelated incident ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP American) (CD 77)) (VP (VBD was) (VP (VBN confirmed) (S (VP (TO to) (VP (VB have) (VP (VBD crashed) (PP (IN in) (NP (DT an) (JJ unrelated) (NN incident))))))))) (. .)))