In 1936, Jan Klint travelled to the USA, where he was employed as an aeronautical engineer with Taylor Aircraft in Pennsylvania. The following year he returned to Denmark, where his task was to set up an assembly plant for Piper-Club aircraft. In May of 1940, his wanderlust once again drew him to the USA, where he continued his education in aircraft engines. He had in the meantime served with the anti aircraft artillery in Esbjerg, and his experiences from then led him to sign on as a volunteer in the US army in 1941. During World War 2, he repaired planes and trained fighter pilots in the USA, and from 1944 onwards he was transferred to active service in North Africa. After the war, he continued his employment with Piper Aircraft, but concurrently also started up a department of Le Klint in the USA.
Upon the death of his father, not only did he become the director of Le Klint, but also of Lactosan in Odense and Ringe. At Lactosan he invented a machine that could crack thousands of eggs automatically, and the patent on this machine occasionally provided some financial help to Le Klint.
Jan Klint initially had no interest in taking over the leadership of Le Klint, but back then, father's word was law, and Tage Klint was a man of the old school who didn't listen much to his children's objections. The directorship of Le Klint also came at a personal cost, as his American wife and three children returned to the USA, as they were unable to settle in in Denmark.
As a businessman, Jan Klint brought an international and American-inspired outlook on business management to Le Klint. Conversely he also had to adapt to the more sedate mentality on Funen. However, Jan Klint became a very beloved director who in time learned to prize people over technology and to understand the good sense in having a good relationship with the employees.