Incident
On September 10, 1976, a mid-air collision occurred near Zagreb, in what is now Croatia. The two aircraft involved were British Airways Flight 476, which was en route from London to Istanbul, and Inex-Adria Aviopromet Flight 550, traveling from Split, then in the Socialist Federal Republic of Yugoslavia, to Cologne, West Germany. The collision took place in the vicinity of Zagreb.
Cause
The collision was attributed to a procedural error on the part of air traffic controllers in Zagreb. This error led to the two flights occupying the same airspace at the same time, resulting in the collision.
Aftermath
The incident prompted reviews of air traffic control procedures. However, no further details regarding specific outcomes or changes are provided in the source.