At 15.43 hours on 16 July 1942, U-161 attacked convoy AS-4 about 500 miles north of St. Thomas, Virgin Islands and observed two hits on a first ship after 2 minutes 32 seconds and heard a third detonation after 3 minutes 35 seconds. Achilles reported one ship sunk and another possible damaged. In fact, only the Fairport was sunk by two torpedoes.

The Fairport (Master George F. Hanock) in station #12 was struck on the port side in the #4 hold by the first torpedo and in the #1 hold about 12 feet below the waterline by the second. The first blew off the #4 hatch cover and started a fire that incoming sea water quickly extinguished. The other torpedo opened up a large hole 30 feet long by 25 feet wide in the hull. The engines were secured immediately and the gun crew fired one shot to indicate the direction of the torpedoes. Five minutes after the hit, all ten officers, 33 crewmen, 14 armed guards (the ship was armed with one 4in, four .50cal and two .30cal guns) and 66 US Army personnel on board abandoned ship in two lifeboats and five rafts. After ten minutes the vessel sank stern first. All survivors were picked up by USS Kearny (DD 432) (LtCdr A.H. Oswald, USN) after the destroyer had dropped depth charges and landed in New York on 21 July.