I’m afraid its for real………not sure of the exact minimum distance before collision avoidance kicks in :shock:
Its a lot more common than ya think :wink:
Don’t want to be a bore, but they are allowed within a kilometre of each other at the same altitude, but they are considered to be in separate airspace if their altitudes are different by 300m.
It used to be 5km or 300 vertical metres, but seems to have been updated by aviation authorities to include anything that ATCs or pilots felt was dangerous.