Aircraft components are mostly made by aluminum alloy as thin wall types. These parts are usually end milled to required thicknesses and tight tolerances in specific areas. The thin wall parts are difficult to machine because they are easy to vibrate and deformed due to their lower rigidity. This paper proposes a new elastic-plastic deformation model which is suitable for prediction of machining deformations of end milled thin wall parts. The theoretical deformation model is established on the basis of the equations of Von Kármán. The effect of bending springback is also taken into account. The part deformations are simulated using FE analysis and Matlab. Milling experiments on a CNC machining center are performed. The experimental results show that the deformations for the peripheral milling of thin wall parts can be captured with very high accuracy using the proposed elastic-plastic deformation prediction model.