 The British fleet left Scapa Flow as a single group on 14 July . During the voyage north , the airmen received detailed briefings on the attack plans and terrain around Kaafjord and were also issued with escape kits to use if they were shot down over Norway . Maintenance personnel also worked to ensure that as many aircraft as possible would be ready . The twelve German submarines in the Norwegian Sea did not make contact with the British force as it sailed north . The weather for much of the voyage was foggy , but the skies were clear when the fleet reached its flying off position to the north of Kaafjord in the evening of 16 July . 
