Concerns over the safety of other aircraft began to mount.
( ( Concerns ( over ( ( the safety ) ( of ( other aircraft ) ) ) ) ) ( ( began ( to mount ) ) . ) )
(ROOT (S (NP (NP (NNS Concerns)) (PP (IN over) (NP (NP (DT the) (NN safety)) (PP (IN of) (NP (JJ other) (NN aircraft)))))) (VP (VBD began) (S (VP (TO to) (VP (VB mount))))) (. .)))
Safety of the other aircraft could be endangered by the proximity of the hijacked plane.
( ( Safety ( of ( the ( other aircraft ) ) ) ) ( ( could ( be ( endangered ( by ( ( the proximity ) ( of ( the ( hijacked plane ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NP (NNP Safety)) (PP (IN of) (NP (DT the) (JJ other) (NN aircraft)))) (VP (MD could) (VP (VB be) (VP (VBN endangered) (PP (IN by) (NP (NP (DT the) (NN proximity)) (PP (IN of) (NP (DT the) (JJ hijacked) (NN plane)))))))) (. .)))