  We show that, contrary to the statements made by many authors, the backflow
is not a nonclassical effect. The backflow is a characteristic feature of
solutions of the wave equations: quantum and classical. We present simple
solutions of the Dirac equation, Maxwell equations and equations of linearized
gravity where the backflow phenomenon is clearly seen. In this work we describe
backflow in relativistic theories but this phenomenon can occur in the
solutions of all kinds of wave equations: quantum and classical.
