[Mikael Olrog]

As pointed out earlier, navigating by night in pre-war times through Europe wouldn't have presented any great challenge for a trained crew. There were numerous scheduled night routes (especially mail-cargo) in operation succesfully for decades before the war broke out. A night flight would not have been identified, even if it was detected (heard) from ground. If the clandestine flight would have been undertaken during day time it is likely that it would have been both detected and acted upon by diplomatic means rather than scrambling a fighter. The day time clandestine reconnaissance flights conducted by e.g. Do 17 R during the Sudeten crisis over central Bohemia was detected and a verbal note was sent to the German foreign ministry from Czechoslovakian authorities. These included also the German civil registration of the aircraft.

Travelling in Europe was not as easy pre-war as it is today and required some paperwork, and it would likely have become tougher after the Sudeten crisis.