Output power and gain saturation characteristics are analyzed for a class of high speed flowing gas molecular lasers. Those flow lasers are treated for which laser action occurs within an optical cavity with an axis transverse to the flow direction, during the vibrational relaxation period following an initial excitation process that takes place upstream of the cavity. Performance predictions for an electrically excited fluid mixing CO2laser based upon recent experimental measurements are presented. The concept of an ``equivalent nonflow laser'' is introduced which facilitates flow laser performance analysis in certain cases.