New Particle Physics above LHC energies? Hints from Ultrahigh Energy Cosmic Rays

I will discuss the physics of UHECR air showers and report how present models tuned at accelerator energies, fail to describe Auger data above E_CM ~ 100 TeV. Possibilities for new physical phenomena which could explain these observations will be described. More detailed studies of UHECR air showers can discriminate between models, as will be explained.