  A disturbing aspect of Hawking's derivation of black hole radiance is the
need to invoke extreme conditions for the quantum field that originates the
emitted quanta. It is widely argued that the derivation requires the validity
of the conventional relativistic field theory to arbitrarily high,
trans-Planckian scales. We stress in this note that this is not necessarily the
case if the question is presented in a covariant way. We point out that Hawking
radiation is immediately robust against an invariant Planck-scale cutoff. This
important feature of Hawking radiation is relevant for a quantum gravity theory
that preserves, in some way, the Lorentz symmetry.
