Cosmic rays with energies exceeding 10^20 eV have been detected thanks to indirect measurements of primary particles by EAS observations. Thanks to increasing number of events registered by
fluorescence observatories like Telescope Array or Pierre Auger Observatory, we can try to solve the main problems in cosmic rays physics. One of them, understanding of the mass composition,
require precise interpretation of measured EAS picture using monte-carlo simulations. Inelastic cross-section for proton-air and nucleus-air is one of parameters plays main role during EAS
development and because of strong impact on X max position is very important for interpretation of mass composition of primary particles. In this work, we present results of mass composition
analysis based on CONEX simulations with three commonly used high energy interaction models - QGSJETII-04, Sibyll2.3c and EPOS-LHC. For simulations we used revised by us inelastic cross-sections extrapolated up to ultra high energies using geometrical model. As a results we present that interpretation of mass composition depends not only on used high energy model or experimental data set, but also on small differences in inelastic cross sections.