(S (S (BASENP (NN One) (JJ possible) (NN explanation)) (VP (VBD had) (VP (ADVP (RB previously)) (VP (VBN been) (VP (VBN suggested) (PP (IN by) (NP (NP (BASENP (DT the) (NN head)) (PP (IN of) (BASENP (DT the) (NNP Garuda) (NNS pilots) (NN association)))) (COMMA ,) (BASENP (NNP Stephanus) (NNP Geraldus))))))))) (PERIOD .))