6m WSPR and aircraft

M0YOU (116km) has been spotted on 6m again this morning. He has also spotted me. On his signals are very clear signs of aircraft reflections with multiple traces visible. I think much of the GDX I am seeing on 10m upwards is due to aircraft. This mode seems good for at least 200km, but is transitory. Sometimes a badly Doppler shifted signal can be very strong but not decode. There are software programs to predict when aircraft will help. Many microwave DXers use such software.