(S (S (BASENP (DT No) (JJ additional) (NNS passengers)) (VP (VP (VBD were) (PP (IN on) (BASENP (NN board)))) (PP (IN for) (NP (BASENP (DT the) (NN flight)) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VBD was) (NP (BASENP (NN part)) (PP (IN of) (BASENP (DT a) (NN maintenance) (NN test) (NN procedure))))))))))) (PERIOD .))