In space missions, when spacecraft travels back to Earth with hypersonic speed, it suffers loss of communications with the ground station, which is called communication blackout, due to the friction between its surface and the surrounding air forming the plasma sheath. This blackout blocks vehicle communications up to 10 minutes depending on the angle of re-entry, shape of vehicle and the atmosphere's properties. This blackout results in loss of control and guidance from the ground station, which is critical for crew safety and the vehicle. In this paper, we used the Drude model to calculate the complex relative permittivity of the plasma sheath, and developed a MATLAB simulation to compute the attenuation coefficient of electromagnetic waves ranging from 1 GHz to 300 GHz, using electron density data derived from NASA's RAM-C flight experiments under different plasma conditions to representing various re-entry phases. The results shows that the attenuation at its peak at S-band, and then drops sharply beyond plasma frequency forming a clear high-frequency window. The same drop with Ka, EHF bands. These findings demonstrate that Ka- band and EHF frequencies represent effective solution to maintain the communications between the spacecraft and ground station during re-entry, offering lower signal attenuation comparing to S and Ku bands................ Keywords:............... Plasma sheath; Communication blackout; Ka-band; Re-entry; Attenuation coefficient.