As a pilot, I have had multiple “near miss” events. Most pilots I know have had similar experiences. Some of these events still scare me today when I think about them, others were less intense and grave, but I also remember all of them…and what they taught me.
A near miss is any unplanned close proximity passing of two or more aircraft. Sometimes one pilot sees the other aircraft and maneuvers away, taking evasive action if you want to be dramatic. Sometimes both pilots see each other and avoid. These kinds of passes happen daily in the airspace structure of the world. Eyeballs, controllers, and new modern electronic detection measures also aid pilots from bending metal in the sky.
But the really scary near misses are the ones that no pilot sees, until it’s too late, or both aircraft safely pass and the pilots become aware of that danger after it has passed. Just knowing how close you came to death, and never recognizing it, is a terrifying thing. Those types of passes will keep you up at night for years to come. Trust me.
You may have read recently that a U.S. coalition aircraft flying over Syria had a near miss with a Russian fighter jet. Some reports have said that the near miss put the two aircraft about a mile apart, while other reports put things a little closer. This close call is said to have been inadvertent, and not an act of aggression by either country. It was an accident.