Summary: An off-line maximum-likelihood identification is described to improve current propeller aircraft models. Additional sensors are used to better define the process and the measurement submodels. The GPS satellite navigation system in differential mode (DGPS) is used to obtain more precise measurement correction values which improve the estimation of wind disturbances. A Pitot tube placed behind the propeller allows a more accurate thrust estimation. Differential pressure sensors placed in the wing improve the lift estimation. The combination of Pitot tube and wing pressure sensors leads to a better separation of the effects of propeller and wing processes. Work is in progress to use these data for the interference modeling of these processes.