The energies of the most energetic extensive air showers observed at the Yakutsk array have been estimated with help of the all detectors readings instead of using of the standard procedure with a parameter s ( 600 ) .
These detector readings have been compared with the detector responses , calculated for all particles which hit the scintillation detectors in each individual shower with observed the zenith and azimuth angles with help of the GEANT4 code .
In turn the code CORSICA-6.616 have been used to produce such particles in the atmosphere in these individual showers and propagate them to detectors at the level of observation .
Calculations have been carried out in terms of the QGSJET-2 and Gheisha-2002 models with the thinning parameter { 10 } ^ { -8 } for the primary protons and helium , oxygen and iron nuclei .
The energy of the most energetic extensive air shower observed at the Yakutsk array happened to be 200 , 200 , 180 and 165 EeV with the values of the { \chi } ^ { 2 } function per one degree of freedom 0.9 , 1. , 0.9 and 1.1 for the primary protons and helium , oxygen and iron nuclei accordingly .
Thus interpreting data in terms of the QGSJET-2 and Gheisha 2002 models we conclude that after the bump and decreasing of the flux of the primary particles due to the Greisen , Zatsepin and Kuzmin effect that has been observed at the HiRes array and at the Pierre Auger observatory there is a possible feature in the energy spectrum – some increase in the flux at energies 200 – 300 EeV observed both at the Yakutsk array and at the AGASA array .
Such possible feature may be understood as the flux of heavy primary nuclei .
It is also not excluded that some new component of the spectrum is observed or the Lorentz invariance may be violated at such huge energies .
As an alternative conclusion the models QGSJET-2 and Gheisha 2002 should be changed so as to produce much more muons in a shower .