A method is disclosed that can include the steps of: in response to a radar stimulator aircraft receiving information for causing it to stimulate a radar system in a user specified manner, the radar stimulator aircraft monitoring the position of an onboard unit thereof relative to at least one antenna of the radar system; and based on the received information and the monitored position of the onboard unit the radar stimulator aircraft controlling its flight and the emission of radar signals thereby to stimulate the radar system in the user specified manner.