Here, we summarize the results of our investigation of means for controlling high-speed flows using helium injection, with particular emphasis on the wavefront distortion of light transmitted through the boundary layer. Quantitative estimates of wavefront distortion were obtained, with and without helium injection, and new diagnostic techniques were developed, including a MHz rate Hartmann wavefront sensor. In particular, we demonstrated the ability to capture real-time wavefront data in two dimensions using an ultra-fast Shack-Hartmann sensor in hypersonic and transonic turbulent boundary layers. These measurements have high temporal resolution (2 μs), while providing full dimensional information on the planar field. Such measurements are vital for making accurate and complete estimates of aero-optic distortion due to boundary layer turbulence in air-borne laser applications, and to assess quantitatively the effectiveness of control methods.