A generalized theory of the Hanle effect is developed for the case of propagation quantum beats. Time-integrated quantum beats of two polariton wave packets with the same group velocities and polarizations belonging to two different Zeeman components in Voigt geometry of the quadrupole-active ortho-exciton Γ₅⁺ level in Cu₂O crystal give rise to the propagation Hanle effect. It is characterized by a quasiresonant dependence of the emitted light intensity on the magnetic field strength, as well as by a supplementary periodic dependence. This dependence originates from the difference of the wave vectors of the carrier waves. It has a period inversely proportional to the sample thickness and can be observed when the propagation way is larger than the light wavelength and the propagation time is shorter than the dephasing time. The interference of two monochromatic waves with the same frequencies and amplitudes but with different polarizations in both Faraday and Voigt geometries is also considered. The dispersion laws of five polariton branches with different polarizations in both geometries are obtained. The theory developed with account of the effective propagation way explains recent experimental results on quantum interference in Cu₂O.