A transverse air jet injected into a Mach 5 model inlet flow generated by an in-draft supersonic wind tunnel, is used to induce inlet unstart. Planar Laser Rayleigh Scattering (PLRS) from condensed CO2 particles in the tunnel flow is used to visualize the unsteady flow during unstart. Simultaneously, pressure traces along the wind tunnel are recorded with high speed pressure sensors attached to the bottom wall of the wind tunnel. A series of time synchronized PLRS images reveals that a shock system, followed by flow separation, originating from the jet injection nozzle propagates upstream. The flow then unstarts upon the arrival of the shock at the inlet. Studies conducted using three different inlet model geometries indicate that the presence of turbulent wall boundary layers strongly affect the unstart dynamics. It is found that relatively thick turbulent boundary layers result in faster inlet unstart, when compared to thin, laminar boundary layers.