On January 6, 1944 U-270 under the command of Oberleutnant Paul Frederick Otto was on its 4th war patrol and was north of the Azores when they were located by a B-17 of R.A.F. Coastal Command 206 Squadron flown by Squadron Leader Anthony J. Pinhorn. The aircraft made two strafing runs, but did not drop any depth charges. On the third run the gunners on U-270 hit the aircraft and sent it crashing into the sea, but not before they dropped a pattern of depth charges, which the U-boat could not avoid. When they exploded the boat was near enough that the concussion put her forward torpedo tubes out of action and the patrol had to be aborted. The boat returned to St. Nazaire on Jan. 17 and did not leave for another patrol until June 6.

This patrol was also ended by an aircraft attack when it was damaged by a Wellington of 172 Squadron R.A.F. But as they were returning to St. Nazaire they were attacked again on June 13 by a B-24 of 53 Squadron R.A.F., this aircraft was also shot down by the gunners on U-270. None of the air crews survived.

Aircraft were the bane of U-boats in the later stages of the war, and for U-270 they would be her end. She was sunk by a Sunderland of 461 Squadron R.A.A.F. on Aug. 13, 1944, none of her crew were lost. U-270 only damaged one ship during her career, this was HMS Lagan K-259 on Sept. 20, 1943, she became a total loss.