Do we observe fluctuation of cross section in cosmic rays ?
  It is known from some time that to explain some apparently {\it exotic events} observed in cosmic ray experiments, a deeply penetrating component in cosmic rays is needed, which, in turn, leads frequently to the nonexponential distributions of some observables. We argue that such unexpected behavior of some cosmic rays data can be most naturally explained by attributing them to the possible fluctuations of cross sections. 
Grzegorz Wilk and Zbigniew Wlodarczyk
astro-ph.HE hep-ph