(S (S (NP (NP (NP (DT The) (NP (NP (BASENP (NNP March) (NN 7)) (COMMA ,) (BASENP (NN 2007))) (NN crash))) (PP (IN of) (BASENP (DT a) (NNP Boeing) (NN 737-400)))) (PP (IN at) (BASENP (NNP Yogyakarta) (NNP International) (NNP Airport)))) (VP (VBD killed) (BASENP (NN 21) (NNS people)))) (PERIOD .))