For a long time the British had struggled to provide air support to convoys crossing the Atlantic, there was a large ‘air gap’ in the middle where no aircraft could operate. The introduction of very long range aircraft, most notably the massive B-24 Liberator started to change the balance of threats in the Battle of the Atlantic. The presence of such aircraft overflying convoys forced U-boats to remain submerged for very much longer, having to proceed more cautiously and much more slowly.
The Liberators also engaged in extremely long hunting sweeps out to sea looking for U-boats. More often than not they endured numerous patrols without seeing anything. Yet after many hours of monotonous visual and radar observation they had to prepared to attack a sighting at a moments notice.
Detecting U-boats leaving France meant that the Bay of Biscay was a favourite hunting ground:
There was an eventful day for the crew of Liberator 1 serial AM924 of 120 Squadron on 11 January 1942, when on detachment at St Eval from Nutts Corner in County Antrim. Flown by
Fg. Off Peter Cundy the Liberator took off at 04.10 hours for a lengthy patrol over the Bay of Biscay. At 15.20 hours, when about 100 miles off the north-west tip of Spain, the crew saw a Heinkel Hel 15 floatplane below and beneath them. Cundy banked to allow his rear and side gunners to open fire, at a distance of 200-600 yd. They scored numerous hits but the enemy aircraft disappeared in a rain squall.
A U-boat and a merchant vessel were spotted about twenty minutes later, about 5 miles off the starboard beam. Cundy climbed to 1,000 ft and then dived, releasing three 250 lb depth charges which straddled the merchant vessel while his front gunner opened fire.
At the same time, the Heinkel reappeared and Cundy turned to attack this aircraft, which took avoiding action. Three more cannon attacks were made on the merchant vessel, interspersed with air combat. The action was eventually broken off owing to shortage of fuel and ammunition.