Longitudinal and transverse dynamics of molten NaCl beyond the hydrodynamic region is studied by generalized collective modes (GCM) analysis of relevant time correlation functions obtained in ab initio molecular dynamics. A comparison with results of rigid-ion treatment of collective dynamics in the molten salt is made. A reduction of the long-wavelength gap between longitudinal and transverse optic-like excitations due to polarization effects is discussed. We propose an analysis, based on analytical expressions for 'bare' propagating collective excitations, that are a generalization of Takeno-Goda formulae for the case of binary disordered system at arbitrary wavenumber. (C) 2008 Elsevier B.V. All rights reserved.