He An air attack against North America may be in progress.
( He ( ( ( An ( air attack ) ) ( against ( North America ) ) ) ( ( may ( be ( in progress ) ) ) . ) ) )
(ROOT (S (NP (PRP He)) (PP (NP (DT An) (NN air) (NN attack)) (IN against) (NP (NNP North) (NNP America))) (VP (MD may) (VP (VB be) (PP (IN in) (NP (NN progress))))) (. .)))
An air attack may have started against the country, the FAA announced.
( ( ( An ( air attack ) ) ( may ( have ( started ( against ( the country ) ) ) ) ) ) ( , ( ( the FAA ) ( announced . ) ) ) )
(ROOT (S (S (NP (DT An) (NN air) (NN attack)) (VP (MD may) (VP (VB have) (VP (VBN started) (PP (IN against) (NP (DT the) (NN country))))))) (, ,) (NP (DT the) (NNP FAA)) (VP (VBD announced)) (. .)))