(S (S (BASENP (DT The) (NNP United) (NNPS States) (NNP Air) (NNP Force)) (VP (ADVP (RB initially)) (VP (VBD said) (SBAR (S (BASENP (NNS witnesses)) (VP (MD must) (VP (VB have) (VP (VBN seen) (NP (BASENP (NNS reflections)) (VP (VBG coming) (PP (IN from) (BASENP (JJ commercial) (NNS airliners))))))))))))) (PERIOD .))