  We show that with GLAST there will be the possibility to detect, within the
UHECR skimming at atmosphere edges, the showers generated by very high energy
upward and horizontal Tau. The effective area, thanks to the large area covered
by the showers at 550 Km, is less than that of AUGER, but its efficiency is
comparable because the lower detection threshold and the consequent event rate
may lead to a few EeV and-or few Glashow resonant signals within a decade.
