Weren't radio communications a big source of intel for the Britts as to where German subs were operating especially early in the war? Wasn't this also the reason the Britts were able to track down most of Bismarck's support ships during and after her raid? I'd think that the planes would have to be making pretty extensive radio contact with the subs for this to work. Not good for either if a Britt DD shows up in the middle of a resupply op.