They were planning to hijack these planes and turn them into large guided missiles, loaded with up to 11,400 gallons of jet fuel.
( They ( ( were ( planning ( to ( ( ( hijack ( these planes ) ) and ) ( ( turn them ) ( into ( ( ( large ( guided missiles ) ) , ) ( loaded ( with ( ( ( ( up to ) 11,400 ) gallons ) ( of ( jet fuel ) ) ) ) ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (PRP They)) (VP (VBD were) (VP (VBG planning) (S (VP (TO to) (VP (VP (VB hijack) (NP (DT these) (NNS planes))) (CC and) (VP (VB turn) (NP (PRP them)) (PP (IN into) (NP (NP (JJ large) (JJ guided) (NNS missiles)) (, ,) (VP (VBN loaded) (PP (IN with) (NP (NP (QP (IN up) (TO to) (CD 11,400)) (NNS gallons)) (PP (IN of) (NP (NN jet) (NN fuel)))))))))))))) (. .)))
Their plan was to hijack the aircraft and use them as missiles.
( ( Their plan ) ( ( was ( to ( ( ( hijack ( the aircraft ) ) and ) ( ( use them ) ( as missiles ) ) ) ) ) . ) )
(ROOT (S (NP (PRP$ Their) (NN plan)) (VP (VBD was) (S (VP (TO to) (VP (VP (VB hijack) (NP (DT the) (NN aircraft))) (CC and) (VP (VB use) (NP (PRP them)) (PP (IN as) (NP (NNS missiles)))))))) (. .)))