A method for estimating the effect of environmental conditions on an aircraft, including measuring the motions of an aircraft; estimating the expected motions of the aircraft, wherein the expected motions of the aircraft are estimated using information regarding the aircraft's control inputs and/or control surface positions; and estimating, based on the measured motions of the aircraft and the expected motions of the aircraft, the forces exerted on the aircraft by the environmental conditions, wherein the forces are estimated based on a difference between the measured motions of the aircraft and expected motions of the aircraft.