At least two callers from the flight reported that the hijackers knew that passengers were making calls but did not seem to care.
( ( ( ( ( At least ) two ) callers ) ( from ( the flight ) ) ) ( ( reported ( that ( ( the hijackers ) ( ( ( knew ( that ( passengers ( were ( making calls ) ) ) ) ) but ) ( ( did not ) ( seem ( to care ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (QP (IN At) (JJS least) (CD two)) (NNS callers)) (PP (IN from) (NP (DT the) (NN flight)))) (VP (VBD reported) (SBAR (IN that) (S (NP (DT the) (NNS hijackers)) (VP (VP (VBD knew) (SBAR (IN that) (S (NP (NNS passengers)) (VP (VBD were) (VP (VBG making) (NP (NNS calls))))))) (CC but) (VP (VBD did) (RB not) (VP (VB seem) (S (VP (TO to) (VP (VB care)))))))))) (. .)))
The hijackers did not care about others making calls. 
( ( The hijackers ) ( ( ( did not ) ( care ( about ( others ( making calls ) ) ) ) ) . ) )
(ROOT (S (NP (DT The) (NNS hijackers)) (VP (VBD did) (RB not) (VP (VB care) (PP (IN about) (NP (NP (NNS others)) (VP (VBG making) (NP (NNS calls))))))) (. .)))