At 9:27, after having been in the air for 45 minutes, United 93 acknowledged a transmission from the Cleveland Center controller.
( ( At 9:27 ) ( , ( ( after ( having ( ( been ( in ( the air ) ) ) ( for ( 45 minutes ) ) ) ) ) ( , ( ( United 93 ) ( ( ( acknowledged ( a transmission ) ) ( from ( the ( Cleveland ( Center controller ) ) ) ) ) . ) ) ) ) ) )
(ROOT (S (PP (IN At) (NP (CD 9:27))) (, ,) (PP (IN after) (S (VP (VBG having) (VP (VBN been) (PP (IN in) (NP (DT the) (NN air))) (PP (IN for) (NP (CD 45) (NNS minutes))))))) (, ,) (NP (NNP United) (CD 93)) (VP (VBD acknowledged) (NP (DT a) (NN transmission)) (PP (IN from) (NP (DT the) (NNP Cleveland) (NNP Center) (NN controller)))) (. .)))
At 9:27, United 93 refused to acknowledge a transmission from the Cleveland Center.
( ( At 9:27 ) ( , ( ( United 93 ) ( ( refused ( to ( ( acknowledge ( a transmission ) ) ( from ( the ( Cleveland Center ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN At) (NP (CD 9:27))) (, ,) (NP (NNP United) (CD 93)) (VP (VBD refused) (S (VP (TO to) (VP (VB acknowledge) (NP (DT a) (NN transmission)) (PP (IN from) (NP (DT the) (NNP Cleveland) (NNP Center))))))) (. .)))