(S (S (BASENP (NNP Urdon)) (VP (VBD said) (SBAR (IN that) (S (NP (BASENP (DT a) (JJ major) (NN part)) (PP (IN of) (BASENP (DT the) (NN problem)))) (VP (VBZ is) (SBAR (IN that) (S (NP (BASENP (NN eight)) (PP (IN of) (NP (BASENP (DT the) (NN company) (POS 's)) (NNS aircraft)))) (VP (VBP are) (NP (BASENP (NNPS MD-11s)) (COMMA ,) (SBAR (WHNP (WDT which)) (S (VP (VBP consume) (NP (BASENP (JJ large) (NNS volumes)) (PP (IN of) (BASENP (NN fuel)))))))))))))))) (PERIOD .))