He was born in Hasbaya, Lebanon. In 1948, he graduated from the Saint Joseph University (Université Saint-Joseph) in Beirut, Lebanon. In 1952, he earned a doctorate in law from the University of Paris, and continued his education at the university's Institute of Higher International Studies. Furthermore, he graduated from the Hague Academy of International Law, and was elected as President of the Association of Attendees and Alumni of the Hague Academy of International Law in 1952.
Returning to Lebanon in 1953, he accepted the post of Chief of Legal Services for International Agreements and External Relations at the Lebanese Directorate of Civil Aviation. In 1956, he became Lebanese Representative to the ICAO Council, serving until 1962. From 1963 to 1964, he served as Chief of Administrative Services for the Lebanese Directorate-General of Transport. In 1965, he was reappointed as Lebanese Representative to the ICAO Council serving until his appointment as the fifth Secretary-General of the ICAO in 1970 and served in that post until his appointment as ICAO Council President. From 1976 to 2006, he served as President of the ICAO Council. He was succeeded in that post by Roberto Kobeh Gonzalez. 
After retiring from active service with ICAO, Kotaite established the Assad Kotaite Graduate and Postdoctoral Fellowship Fund. This scholarship programme acknowledges the importance of assistance and cooperation in the field of specialized aviation training, with the objective of advancing the safety and development of civil aviation by strengthening the capabilities of national civil aviation personnel.
Awards and honors
- After retirement, he was named President Emeritus of the International Civil Aviation Organization (ICAO)
- Recipient of the 2005 Philip J. Klass Award for Lifetime Achievement
- In September 2013, he received the highest honour in the world of civil aviation, the Edward Warner Award