Allied convoys to Northern Russia during WWII were under the constant
surveillance of Luftwaffe aircraft including Bv138 flying boats as
depicted here. The 'eyes of the U-Boat arm', these aircraft were commonly
refuelled at sea by German submarines, usually in remote coastal locations
in the North Atlantic and Baltic. In this painting, a Type VIIC
U-Boat gently draws alongside a "Flying Clog" of one of
the 'See Aufklarungsgruppen' in 1943.
Considering the nature of their task, those guys on the conning tower
should really put out their cigarettes !