That message and all subsequent attempts to contact the flight were not acknowledged.
( ( ( ( That message ) and ) ( ( all ( subsequent attempts ) ) ( to ( contact ( the flight ) ) ) ) ) ( ( ( were not ) acknowledged ) . ) )
(ROOT (S (NP (NP (DT That) (NN message)) (CC and) (NP (NP (DT all) (JJ subsequent) (NNS attempts)) (SBAR (S (VP (TO to) (VP (VB contact) (NP (DT the) (NN flight)))))))) (VP (VBD were) (RB not) (VP (VBN acknowledged))) (. .)))
That message was acknowledged with a prompt reply.
( ( That message ) ( ( was ( acknowledged ( with ( a ( prompt reply ) ) ) ) ) . ) )
(ROOT (S (NP (DT That) (NN message)) (VP (VBD was) (VP (VBN acknowledged) (PP (IN with) (NP (DT a) (JJ prompt) (NN reply))))) (. .)))