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 asked planes to protect the cockpits immediately using the Air Marshalls on board.
( ( FAA controllers ) ( ( ( asked planes ) ( to ( ( ( protect ( the cockpits ) ) immediately ) ( ( using ( the ( Air Marshalls ) ) ) ( on board ) ) ) ) ) . ) )
(ROOT (S (NP (NNP FAA) (NNS controllers)) (VP (VBD asked) (NP (NNS planes)) (S (VP (TO to) (VP (VB protect) (NP (DT the) (NNS cockpits)) (ADVP (RB immediately)) (S (VP (VBG using) (NP (DT the) (NNP Air) (NNPS Marshalls)) (PP (IN on) (NP (NN board))))))))) (. .)))