A method for delivering a load to a target, the load being releasably attached to an unmanned aircraft , the unmanned aircraft comprising one or more processors , the method comprising: acquiring, by the one or more processors , a position of the target on the ground ; acquiring, by the one or more processors , parameter values relating to manoeuvrability of the aircraft ; acquiring, by the one or more processors , one or more properties of the load ; acquiring, by the one or more processors , parameter values relating to environmental conditions in which the aircraft is flying; using the acquired target position, the acquired load properties, and the acquired parameter values relating to the environmental conditions, calculating, by the one or more processors , a payload release location for the aircraft and a value of a payload release velocity for the aircraft ; using the determined payload release location and payload release velocity value, determining, by the one or more processors , a procedure for the aircraft ; performing, by the aircraft , the determined procedure; and at a point in the procedure that the aircraft has the determined payload release location and a velocity equal to the determined payload release velocity value, releasing, by the aircraft , the load ; wherein the determined payload release location and payload release velocity value are such that, were the aircraft to release the load whilst located at the determined payload release location and travelling at a velocity equal to the determined payload release velocity value, the load would land on the ground within a predetermined distance of the target; and the determined procedure is such that, were the aircraft to perform that procedure, at at least one instance during the procedure, the aircraft would be located at the determined payload release location and be travelling at a velocity equal to the determined payload release velocity value. acquiring, by the one or more processors , a position of the target on the ground ; acquiring, by the one or more processors , parameter values relating to manoeuvrability of the aircraft ; acquiring, by the one or more processors , one or more properties of the load ; acquiring, by the one or more processors , parameter values relating to environmental conditions in which the aircraft is flying; using the acquired target position, the acquired load properties, and the acquired parameter values relating to the environmental conditions, calculating, by the one or more processors , a payload release location for the aircraft and a value of a payload release velocity for the aircraft ; using the determined payload release location and payload release velocity value, determining, by the one or more processors , a procedure for the aircraft ; performing, by the aircraft , the determined procedure; and at a point in the procedure that the aircraft has the determined payload release location and a velocity equal to the determined payload release velocity value, releasing, by the aircraft , the load ; wherein the determined payload release location and payload release velocity value are such that, were the aircraft to release the load whilst located at the determined payload release location and travelling at a velocity equal to the determined payload release velocity value, the load would land on the ground within a predetermined distance of the target; and the determined procedure is such that, were the aircraft to perform that procedure, at at least one instance during the procedure, the aircraft would be located at the determined payload release location and be travelling at a velocity equal to the determined payload release velocity value. <EOS>