(S (S (BASENP (PRP He)) (VP (ADVP (RB also)) (VP (VBD said) (SBAR (IN that) (S (S (BASENP (PRP it)) (VP (VBD was) (VP (VBN pursued) (PP (IN by) (BASENP (NN two) (NN fighter) (NNS jets)))))) (COMMA ,) (SBAR (WHADVP (WRB when)) (S (BASENP (PRP it)) (VP (VBD disappeared) (PP (IN at) (NP (BASENP (DT a) (NN speed)) (SBAR (S (BASENP (PRP he)) (VP (VBD estimated) (S (VP (TO to) (VP (VB be) (BASENP (NN 3,000) (NN mph)))))))))))))))))) (PERIOD .))