Following recent proof of swept wing laminar-to-turbulent boundary layer transition delay through base-flow modification using AC-DBD plasma actuators, an experimental investigation is performed to study the responsible physical mechanism. An experiment is conducted on a 45° swept wing in the anechoic wind tunnel at the Delft University of Technology. Stereoscopic PIV is employed to study the influence of the AC-DBD plasma actuator on the boundary layer velocity profiles. It is found that the AC-DBD plasma actuator is capable of directly decreasing the cross-flow component for various operating conditions. Moreover, as the Reynolds number is decreased, the authority of the actuator increases accordingly. In a second wind tunnel experiment in the same facility, the influence of the actuator on the cross-flow instability is monitored by performing 2D2C-PIV measurements at consecutive chord locations. As a result of the body force induced by the actuator, the cross-flow vortices shift position and feature a reduction in amplitude for the high frequency case of 5 kHz. Lower carrier frequencies are found to induce turbulent wedges due to the presence of strong localised plasma discharges. As a consequence, successful cross-flow instability control highly depends on the chosen carrier frequency and voltage, as well as the actuator lifetime and configuration. Although the changes in the transition front can not be observed here due to the consulted wing model, it is believed that the presented results provide an adequate overview of the influence of the AC-DBD plasma actuator on the cross-flow instability and add to the body of knowledge concerning AC-DBD plasma actuators and their application as flow control devices.