At 9:57, the passenger assault began.
( ( At 9:57 ) ( , ( ( the ( passenger assault ) ) ( began . ) ) ) )
(ROOT (S (PP (IN At) (NP (CD 9:57))) (, ,) (NP (DT the) (NN passenger) (NN assault)) (VP (VBD began)) (. .)))
The passengers started fighting back at 9.57 but were quickly subdued.
( ( The passengers ) ( ( ( ( started ( ( fighting back ) ( at 9.57 ) ) ) but ) ( were ( quickly subdued ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS passengers)) (VP (VP (VBD started) (S (VP (VBG fighting) (PRT (RP back)) (PP (IN at) (NP (CD 9.57)))))) (CC but) (VP (VBD were) (VP (ADVP (RB quickly)) (VBN subdued)))) (. .)))