White was considered the best colour for aircraft hunting U boats in the usually cloudy Atlantic. RAF Coastal Command Wellingtons, Liberators, Catalinas and Sunderlands were often painted white underneath, also some USN and USAAF aircraft in the Atlantic too. Even at night a U boat's first sight of an attacking aircraft was its dark silhouette against the clouds and painting them white reduced this.
The RN's carrier-borne aircraft were not generally painted in this scheme however. 835 NAS painted their aircraft white while at sea protecting a convoy and without permission from anyone ashore.
