Controlling aircraft inerting system

A method of controlling an inerting system of an aircraft, wherein the inerting system feeds inert gas into a fuel tank of the aircraft, the method comprising: a) obtaining a location of the aircraft, the location comprising a current location or an expected future location; b) assessing an environmental impact of releasing of fuel vapour at the location obtained in step a); and c) controlling the inerting system based on the assessment of step b). The location may comprise a global location or altitude. In step a) obtaining an expected future location may comprise receiving a flight plan comprising a series of expected future locations of the aircraft, and step b) may comprise assessing an environmental impact of releasing fuel vapour at each future location. Controlling the inerting system may comprise increasing and/or decreasing a flow rate of inert gas into the fuel tank. Also disclosed is an aircraft comprising: a fuel tank 20; an inerting system 8 configured to feed inert gas into the fuel tank; and an automated control system 5 coupled to the inerting system and configured to control the inerting system using the method described.