1. A method for estimating a future change in operation of a monitored aircraft , including at computer on board the monitored aircraft the steps of: calculating a current state of the monitored aircraft from measurements of variables related to operation of the monitored aircraft, sending a request to analyse the similarity of the calculated current state with previous states of aircraft similar to the monitored aircraft, receiving and analysing a change in operation of each similar aircraft having a previous state similar to the calculated current state to determine a probable change in the operation of the monitored aircraft.