(S (S (NP (NP (JJS Most) (BASENP (JJ major) (NN flight) (NNS zones))) (PP (IN from) (NP (BASENP (JJ urban) (NNS centers)) (PP (IN in) (BASENP (NNP Canada)))))) (VP (VBP are) (PP (IN in) (NP (NP (BASENP (PRPD its) (JJ southern) (NN portion)) (COMMA ,) (ADJP (JJ close) (PP (TO to) (BASENP (DT the) (NNP U.S.))))) (SBAR (WHADVP (WRB where)) (S (BASENP (JJ even) (NNS winds)) (VP (MD might) (VP (VP (VB push) (BASENP (DT a) (NN plane))) (PP (IN across) (BASENP (DT the) (NN border))))))))))) (PERIOD .))