Range Doppler imaging, a basic method used in inverse synthetic aperture radar (ISAR), is based on the uniform rotation model of a target. The rotation velocity and axis of a maneuvering aircraft often vary with time. Traditional imaging methods may blur the target image and even render it beyond recognition. A concept is presented for range- instantaneous Doppler imaging and a corresponding imaging method that can clearly improve the image quality of most maneuvering aircraft. The resulting images of real data show that the method is effective.