(S (S (BASENP (DT The) (NNP NTSB)) (VP (VBD suggested) (SBAR (S (BASENP (DT this)) (VP (MD should) (VP (VB be) (UCP (CC either) (UCP (BASENP (DT the) (JJ next) (NN maintenance) (NN check)) (CC or) (PP (IN within) (BASENP (NN six) (NNS months))))))))))) (PERIOD .))