  We study possible Lorentz violations by means of gamma-ray bursts (GRB) with
special focus on the Large Array Telescope (LAT) of GLAST. We simulate bursts
with gtobssim and introduce a Lorentz violating term in the arrival times of
the photons. We further perturb these arrival times and energies with a
Gaussian distribution corresponding to the time resp. energy resolution of
GLAST. We then vary the photon flux in gtobssim in order to derive a relation
between the photon number and the standard deviation of the Lorentz violating
term. We conclude with the fact that our maximum likelihood method as first
developed in [1] is able to make a statement whether Nature breaks the Lorentz
symmetry if the number of bursts with known redshifts is of the order of 100.
