In the past, Ant Colony Optimization (ACO) methods were used to solve combinatorial optimization problems such as the well-known Traveling Salesman Problem. The present article introduces an extension of the ACO method that is capable of solving optimization problems involving free variables with continuous search spaces. To this purpose, various notions, which are implicit in the ACO techniques, have been modified in order to account for design parameters that may vary continuously between lower and upper user-defined bounds. The intention was to create a tool for a particular class of engineering problems, namely the inverse design of isolated or turbomachinery blade airfoils and to demonstrate its effectiveness. Computational Fluid Dynamics codes are used for the evaluation of candidate solutions.