(S (S (PP (IN On) (BASENP (NNP Monday))) (COMMA ,) (S (BASENP (NN travel)) (VP (VP (VBD proved) (ADJP (JJ difficult))) (COMMA ,) (SBAR (IN with) (S (NP (BASENP (NNS flights)) (PP (IN from) (NP (NP (NP (NP (NP (NP (BASENP (NNP Philadelphia)) (COMMA ,) (BASENP (NNP Newark))) (COMMA ,) (BASENP (NNP New) (NNP York) (NNP City))) (COMMA ,) (NNP Hartford)) (COMMA ,) (BASENP (NNP Boston))) (COMMA ,) (BASENP (NNP Portland))) (CONJP (COMMA ,) (CC and)) (BASENP (NNP Washington) (COMMA ,) (NNP D.C.))))) (VP (VBN canceled))))))) (PERIOD .))