1. A system for generating in an aircraft in flight a display indicative of feasibility of a weapon carried on the aircraft successfully engaging a determined target, the system comprising: a first generator for generating a database describing a weapon performance envelope; a second generator for creating coefficients characteristic of that performance envelope using a generic algorithm; an uploader for uploading the coefficients to the aircraft; and a reconstructor for placement on the aircraft and containing the generic algorithm and adapted to select the coefficients for the algorithm according to the aircraft and target conditions in order to generate a feasibility display, wherein the algorithm is generic to both air to ground and air to air weapons.