Disclosed is a system and method for generating, in an aircraft (1) in flight, a display indicative of the feasibility of a weapon carried on the aircraft (1) successfully engaging a determined target (5, T) and/or the feasibility of a weapon carried on the target (5, T) successfully engaging the aircraft (1). The method comprises: using a performance envelope of the weapon and performance envelope(s) for one or more different types of aircraft (1), determining a further performance envelope specifying the performance of the weapon when carried by any of the different aircraft (1) types; determining coefficients for a generic polynomial that fit the generic polynomial to the further performance envelope; uploading, to the aircraft (1), the generated coefficients; and, on the aircraft (1), reconstructing the further performance envelope and generating the feasibility display.