(S (S (BASENP (NNPS Raptors)) (VP (VBD were) (VP (VP (VP (VP (VBN grounded) (ADVP (RBR nationwide))) (PP (IN for) (BASENP (NN five) (NNS months)))) (BASENP (JJ last) (NN Summer))) (PP (IN over) (BASENP (DT the) (NN oxygen) (NNS systems)))))) (PERIOD .))