The New York Center controller and manager were unaware that American 11 had already crashed.
( ( ( ( The ( New ( York ( Center controller ) ) ) ) and ) manager ) ( ( ( were unaware ) ( that ( ( American 11 ) ( ( had already ) crashed ) ) ) ) . ) )
(ROOT (S (NP (NP (DT The) (NNP New) (NNP York) (NNP Center) (NN controller)) (CC and) (NP (NN manager))) (VP (VBD were) (ADJP (JJ unaware)) (SBAR (IN that) (S (NP (NNP American) (CD 11)) (VP (VBD had) (ADVP (RB already)) (VP (VBN crashed)))))) (. .)))
The controllers didn't know that American 11 was already crashed.
( ( The controllers ) ( ( ( did n't ) ( know ( that ( ( American 11 ) ( was ( already crashed ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS controllers)) (VP (VBD did) (RB n't) (VP (VB know) (SBAR (IN that) (S (NP (NNP American) (CD 11)) (VP (VBD was) (ADJP (RB already) (JJ crashed))))))) (. .)))