  In this paper we discuss the problem, why the use of the direct data on
primary nuclei spectra together with the modern hadronic interaction models
leads to significant deficit of computed vertical muon flux at sea level for
energies $>100$ GeV. We suggest, that to find out the source of this
inconsistency it is necessary to perform an analysis of sensitivity of emulsion
chamber data to variations of hadron-nucleus interaction characteristics. Such
analysis will give more ground for discussion of adequacy of the up-to-date
interaction models and of mutual compatibility of primary nuclei spectra,
obtained in direct and EAS experiments.
