(S (S (BASENP (PRP They)) (VP (VBP have) (VP (ADVP (RB also)) (VP (VBN confirmed) (SBAR (IN that) (S (SBAR (IN while) (S (BASENP (NN ice)) (VP (MD may) (VP (VB have) (VP (VBN formed) (ADVP (ADVP (RB elsewhere)) (PP (IN in) (NP (BASENP (DT the) (NN airliner) (POS 's)) (BASENP (NN fuel) (NN system)))))))))) (S (BASENP (NN fuel)) (VP (VBD was) (VP (ADVP (RB probably)) (VP (ADVP (RB not)) (VP (VBN restricted) (PP (IN at) (BASENP (DT any) (JJ other) (NN location)))))))))))))) (PERIOD .))