They knew American 77 was lost.
( They ( ( knew ( ( American 77 ) ( was lost ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD knew) (SBAR (S (NP (NNP American) (CD 77)) (VP (VBD was) (VP (VBN lost)))))) (. .)))
They did not know what had happened to American 77.
( They ( ( ( did not ) ( know ( what ( had ( happened ( to ( American 77 ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD did) (RB not) (VP (VB know) (SBAR (WHNP (WP what)) (S (VP (VBD had) (VP (VBN happened) (PP (TO to) (NP (NNP American) (CD 77))))))))) (. .)))