Technic of air shower observations enables us to cover huge effective area in high-energy cosmic ray
observations. To interprete the observed shower particles to the primary information, we need a help
of Monte Carlo simulation, where a hadronic interaction model is assumed. Because the collision energy
relevant to the CR-air interaction is beyond the accelerator energy, and/or particle production relevant to
the air shower development is not measured by the usual collider experiments, the hadronic interaction
is described by various models that causes uncertainty in the interpretations. The Large Hadron Collider
forward (LHCf) and the Relativistic Heavy Ion Collider forward (RHICf) are the dedicated experiments to
measure forward particle production at the comic-ray equivalent energies between 10^14eV and 10^17eV.
In this seminar, outline and important results of LHCf the RHICf are presented together with the prospects
of ongoing analyses.