FAA controllers at Boston Center, which had tracked the first two hijackings, requested at 9:07 that Herndon Command Center get messages to airborne aircraft to increase security for the cockpit.
( ( ( ( ( ( FAA controllers ) ( at ( Boston Center ) ) ) , ) ( which ( had ( tracked ( the ( first ( two hijackings ) ) ) ) ) ) ) , ) ( ( ( requested ( at 9:07 ) ) ( that ( ( Herndon ( Command Center ) ) ( ( ( get messages ) ( to ( airborne aircraft ) ) ) ( to ( ( increase security ) ( for ( the cockpit ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP FAA) (NNS controllers)) (PP (IN at) (NP (NNP Boston) (NNP Center))) (, ,) (SBAR (WHNP (WDT which)) (S (VP (VBD had) (VP (VBN tracked) (NP (DT the) (JJ first) (CD two) (NNS hijackings)))))) (, ,)) (VP (VBD requested) (PP (IN at) (NP (CD 9:07))) (SBAR (IN that) (S (NP (NNP Herndon) (NNP Command) (NNP Center)) (VP (VBP get) (NP (NNS messages)) (PP (TO to) (NP (JJ airborne) (NN aircraft))) (S (VP (TO to) (VP (VB increase) (NP (NN security)) (PP (IN for) (NP (DT the) (NN cockpit)))))))))) (. .)))
FAA controllers told planes there was no reason to worry.
( ( FAA controllers ) ( ( told ( planes ( there ( was ( no ( reason ( to worry ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP FAA) (NNS controllers)) (VP (VBD told) (SBAR (S (NP (NNS planes)) (ADVP (RB there)) (VP (VBD was) (NP (DT no) (NN reason) (S (VP (TO to) (VP (VB worry))))))))) (. .)))