It was proposed by Haisch, Rueda and Puthoff (Phys. Rev. A, 49, 678, 1994) that the inertia of matter could be interpreted at least in part as a reaction force originating in interactions between the electromagnetic zero-point field (ZPF) and the elementary charged consitutents (quarks and electrons) of matter. Within the limited context of that analysis, it appeared that Newton’s equation of motion, f=ma, could be inferred from Maxwell’s equations as applied to the ZPF, i.e. the stochastic electrodynamics (SED) version of the quantum vacuum. We report on a new approach which avoids the ad hoc particle-field interaction model (Planck oscillator) of that analysis, as well as its concomitant formulational complexity. Instead, it is shown that a non-zero ZPF momentum flux arises naturally in accelerating coordinate frames from the standard relativistic transformations of electromagnetic fields. Scattering of this ZPF momentum flux by an object will yield a reaction force that may be interpreted as a contribution to the object’s inertia. This new formulation is properly covariant yielding the relativistic equation of motion. Our approach is related by the principle of equivalence to Sakharov’s conjecture of a connection between Einstein action and the vacuum. If correct, this concept would substitute for Mach’s principle and imply that no further mass-giving Higgs-type fields may be required to explain the inertia of material objects, although extensions to include the zero-point fields of the other fundamental interactions may be necessary for a complete theory of inertia.