Ah great, thank you both for the links!
I tried the log thing and it seems that the problem comes from the stationary.ini file.
Here are the last lines of my log file:
begin: PlMisStatic: class 'vehicles.planes.LEOStatic$Leo_451' not found
java.lang.RuntimeException: PlMisStatic: class 'vehicles.planes.LEOStatic$Leo_451' not found
at com.maddox.il2.builder.PlMisStatic.configure(PlMisStatic.java)
at com.maddox.il2.builder.Plugin.loadAll(Plugin.java)
at com.maddox.il2.builder.Builder.<init>(Builder.java)
at com.maddox.il2.gui.GUIBuilder.<init>(GUIBuilder.java:73)
at com.maddox.il2.gui.GUI.create(GUI.java:164)
at com.maddox.il2.game.Main3D.beginApp(Main3D.java:701)
at com.maddox.il2.game.Main3D.beginApp(Main3D.java:358)
at com.maddox.il2.game.MainWin3D.beginApp(MainWin3D.java:211)
at com.maddox.il2.game.Main.exec(Main.java:428)
at com.maddox.il2.game.GameWin3D.main(GameWin3D.java:235)
[29 mars 13 17:03:08] -------------- END log session -------------
Don't know what to do though?