Abstract This paper reports further work on the design of feedback control schemes for boundary layer transition control, i.e. the use of feedback control laws to delay the transition from laminar to turbulent flow and thereby achieve an overall reduction in the drag force acting on an aircraft. Previous work has shown that this is a feasible problem - both in theory and, more importantly, in practice where this conclusion has been reached on the basis of wind tunnel test results for cases with gradient based controllers designed on the basis of a local linear model identified about selected operating points. This paper reports further developments on controller design for cases where the local linear model approach fails to provide acceptable control because such models are not an adequate approximation to the process dynamics. by the development of nonlinear cost functions and the use of stochastic optimisation techniques to find the corresponding controllers