Ionic-wind propulsion systems are an alternative to conventional air propulsion technologies, without pollutants, noise emissions, and moving parts. The systems exhibit an emitting electrode placed upstream from a wing, which acts as the collecting electrode. The corona discharge near the emitting electrode, caused by high voltage applied between the electrodes, produces nitrogen ions, which are accelerated towards the collecting electrode by the Coulomb force and captured there. Momentum transfer from the ions to the ambient air induces an air motion known as the “ionic wind”. Since the invention of this technique in 1928 [1], it was studied to a limited extent, with little account for a free-stream influence on the system performance [2,3]. The present study analyzes experimentally and numerically an ionic-wind propulsion system under free-stream flow conditions, and extends previous investigations by accounting for aerodynamic drag as well as for the convective and diffusive influences on the electrical charge transport. The numerical simulations solve the balance equations for mass, momentum and electrical charge, involving Gauss’s law and a relation for predicting corona discharge. The coupling of the flow field with the charge transport is accounted for. The results show an acceleration of the airflow between the emitting and collecting electrodes, which represents a thrust. Increasing free-stream velocities result in higher electric currents due to an enhanced rate of charge transport. The predicted discharge characteristics of the system show good agreement with measurements on a model system in a wind-tunnel. The experiments include wake velocity and high-frequency surface pressure measurements, which show suppressed flow separation under ionic-wind conditions. The findings show that ionic-wind systems perform better under free-stream conditions than suggested by earlier studies without account for charge convection. A potential for application of the technique for active flow control on aircraft wings or on wind turbine blades emerges.