This was later determined to have been Flight 77.
( This ( ( ( was later ) ( determined ( to ( have ( been ( Flight 77 ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBD was) (ADVP (RB later)) (VP (VBN determined) (S (VP (TO to) (VP (VB have) (VP (VBN been) (NP (NNP Flight) (CD 77)))))))) (. .)))
This was determined to be Flight 77 at a later time.
( This ( ( was ( determined ( to ( be ( ( Flight 77 ) ( at ( a ( later time ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (DT This)) (VP (VBD was) (VP (VBN determined) (S (VP (TO to) (VP (VB be) (NP (NP (NNP Flight) (CD 77)) (PP (IN at) (NP (DT a) (JJ later) (NN time))))))))) (. .)))