FAA headquarters had by this time established an open line of communication with the Command Center at Herndon and instructed it to poll all its centers about suspect aircraft.
( ( FAA headquarters ) ( ( ( had ( by ( this time ) ) ) ( ( ( ( ( established ( ( an ( open line ) ) ( of communication ) ) ) ( with ( the ( Command Center ) ) ) ) ( at Herndon ) ) and ) ( instructed ( it ( to ( ( poll ( all ( its centers ) ) ) ( about ( suspect aircraft ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP FAA) (NNS headquarters)) (VP (VBD had) (PP (IN by) (NP (DT this) (NN time))) (VP (VP (VBN established) (NP (NP (DT an) (JJ open) (NN line)) (PP (IN of) (NP (NN communication)))) (PP (IN with) (NP (DT the) (NNP Command) (NNP Center))) (PP (IN at) (NP (NNP Herndon)))) (CC and) (VP (VBN instructed) (S (NP (PRP it)) (VP (TO to) (VP (VB poll) (NP (PDT all) (PRP$ its) (NNS centers)) (PP (IN about) (NP (NN suspect) (NN aircraft))))))))) (. .)))
The line of communication between Herndon and the FAA headquarters was via telephone.
( ( ( The line ) ( of ( communication ( between ( ( Herndon and ) ( the ( FAA headquarters ) ) ) ) ) ) ) ( ( was ( via telephone ) ) . ) )
(ROOT (S (NP (NP (DT The) (NN line)) (PP (IN of) (NP (NP (NN communication)) (PP (IN between) (NP (NP (NNP Herndon)) (CC and) (NP (DT the) (NNP FAA) (NN headquarters))))))) (VP (VBD was) (PP (IN via) (NP (NN telephone)))) (. .)))