(S (S (BASENP (DT The) (NNP US)) (VP (VBZ has) (VP (VP (VBN increased) (BASENP (PRPD its) (NN airport) (NN security))) (PP (VBG following) (NP (NP (BASENP (DT the) (JJ failed) (VBN attempted) (NNP December) (NN 25) (NN bombing)) (PP (IN of) (BASENP (DT a) (NNP Delta) (NN flight)))) (PP (IN by) (NP (BASENP (DT a) (JJ Nigerian) (NN man)) (PP (IN with) (S (BASENP (NN explosives)) (PP (IN in) (BASENP (PRPD his) (NNS underpants)))))))))))) (PERIOD .))