High energy extension of the FLUKA atmospheric neutrino flux

The atmospheric neutrino flux calculated with FLUKA was originally limited to 100-200 GeV for statistical reasons. In order to make it available for the analysis of high energy events, like upward through-going muons detected by neutrino telescopes, we have extended the calculation so to provide a reliable neutrino yield per primary nucleon up to about 10**6 GeV/nucleon, as far as the interaction model is concerned. We point out that the primary flux model above 100 GeV/nucleon still contributes with an important systematic error to the neutrino flux.