Leavitt joined No 617 (Dambuster) Squadron in September 1944. His first two operations after arriving were against Tirpitz, which was sheltering in the fjords of northern Norway. On October 29 1944 he flew as the second pilot with an experienced captain. Over the target, their Lancaster was hit by the battleship's anti-aircraft fire, which hit one of the fuel tanks. Running very short of fuel, the two pilots made a forced-landing at an airfield in the Shetlands.
On November 11, Leavitt piloted one of 31 Lancasters that mounted a second attack against "The Beast", a name given to Tirpitz by Winston Churchill. After taking off at night from an airfield in northern Scotland, Leavitt headed for the rendezvous near the Norwegian/Swedish border. At dawn, he saw flak ahead and skirted its position. He commented: "The terrain below was precipitous and barren, and at the same time magnificent. I have never felt so completely alone in my life."
Leavitt dropped his "Tallboy" bomb from 15,000ft a minute after the leader (Wing Commander "Willie" Tait). His aimer saw the 12,000lb bomb drop into the centre of the smoke erupting from the battleship. A short time later, Tirpitz capsized with large loss of life.
Leavitt also attacked the naval pens at Bremen, Ijmuiden, and Hamburg. On March 27, flying a specially modified Lancaster, he dropped a 22,000lb "Grand Slam" deep penetration bomb on the U-boat construction pens at Farge.
His 21st and final operation was against Hitler's southern redoubt at Berchtesgaden on April 25. Snow on the ground prevented his bomb aimer from identifying the target and their Tallboy was dropped on a viaduct spotted on the return route.
After the war he remained in the RAF and continued to fly Lancasters until he retired as a flight lieutenant in September 1946 and returned to the USA.
John Howland Leavitt was born, during a Zeppelin raid, in Paris on February 6 1918. His American father later served as a US Consular translator to the Versailles Treaty. His mother was English. He was named John Howland after an ancestor who had arrived in America on the Mayflower with the Pilgrims in 1620; after education in Turkey he returned with his parents to the US, attending Darien High School, Connecticut, where his peers elected him the student most likely to succeed.
A graduate of Brown University, Rhode Island, Leavitt was back in Turkey teaching English at Robert College when Britain declared war in 1939. Keen to get involved, he volunteered to fly with the RAF, applying through the British Consulate in Istanbul.
He trained as a pilot in Rhodesia and South Africa before heading to England to convert to the Lancaster. After the attack on Pearl Harbor he applied for a transfer to the USAAC, but on being told that this would require him to repeat all his training, he opted to remain with the RAF.
At the end of the war, he joined the Office of Strategic Services (OSS), forerunner of the CIA, as an intelligence analyst, specialising in Middle Eastern issues and drafting National Intelligence Estimates, including his favourite assessment in the early 1950s – that it would be a long time before the Arabs and Israelis saw eye-to-eye on any issue.
Soon after, he transferred to the CIA's Directorate of Operations and joined the Agency's campaign to reinstate the Shah in Iran. He spent 15 of his 30 years of service at US embassies in Tehran, Athens, Ankara and Tel Aviv. Though he retired in 1978, he returned to the Agency to assist with the Iran Hostage Crisis and the bombing of the American Embassy in Beirut in 1983.
In retirement Leavitt travelled widely to visit his large extended family. A keen golfer, he enjoyed partnering his wife, who played to county level.
John Leavitt died on December 31. He was married to his first wife, Lilias, an English WAAF signals officer whom he met at RAF Waddington during the war, from 1945 until her death in 1972. After a brief second marriage, he married his third wife, Judy, also a former WAAF, whom he met at a 617 Squadron reunion at Woodhall Spa in 1983. She died in 2003. He is survived by two sons and two daughters from his first marriage.