An illustration of the confusion.
Back in nineteen canteen an early arriving Tradewinds CL44 was in the hold at Beek, waiting for the field to open. Amsterdam instructed him to squawk A21. At that time A31 was used for unlawful interference and according to Sod's Law that was selected. Much questioning about Ops. Normal, misreading of transponder setting by the crew, and general hilarity as the Mil struggled to get something airborne (it was a mid summer Sunday morning). Airport manager added to the fun by refusing landing permission. Eventually things quietened down and he landed to be surrounded by all available police and military units.
For all concerned there was neither coffee nor biscuits for the rest of the morning
