In his will, Onassis appointed Ioannidis a lifetime member of the board of directors of the
Onassis Foundation, established in December 1975. He served as Vice President of both the commercial and public benefit foundations until 2005. He also served as Chairman of the Board of all companies owned by
Christina Onassis and was one of the executors of her will. From 1975 to 1984 he was involved with the business activities of the Onassis Foundation, eventually becoming chief executive officer of shipping and commercial operations, an office held until 1995. He was on the board of directors of the
Union of Greek Shipowners from 1979 to 2005, including six years as vice-president and 14 years as president of its training committee. He was named member emeritus in 2000. He was also on the board of the
Hellenic Marine Environment Protection Association (HELMEPA), chairing its training committee for nine years and serving as vice-president for one year. In these roles at the three organisations he introduced the "Airline Concept" to the Greek shipping industry for the first time. Ioannidis was also a member of the
American Bureau of Shipping (ABS) from 1990, serving on its council from 1992, a member of its board of directors for 10 years, and chair of the bureau's Greek National Committee for 10 years. He was named council emeritus in 2004. He was also a member of the
UK P&I Club for eight years. ==Awards and recognition==