Alan says, "When we want to sink a convey, we send out an observation plane first. It is ostensibly an observation plane. Of course, to observe is not its real duty - We already know exactly where the convoy is. Its real duty is to be observed - That is, to fly close enough to the convoy that it will be noticed by the lookouts on the ships. The ships will then send out a radio message to the effect that they have been sighted by an Allied observation plane. Then, when we come round and sink them, the Germans will not found it suspicious - At least, not quite so monstrously suspicious that we knew exactly where to go."