As I understand it (correct me if I'm wrong), "standard" radar spacing for aircraft en route is approximately 2 miles laterally, 5 miles behind and 1,000 ft. vertically. Does anyone know if there are international standards for this, and whether it applies during VFR flight?

The reason I ask is that I had the sighting of a lifetime just moments ago aboard QR719 over Iran en-route from DOH-SEA. A Mahan Air A340-600 operating as W563 from IKA-DXB passed in the other direction, with the aircraft for a split second occupying nearly the entire width of my window view from 10A. I am in a rear-facing seat so maintained visual for probably just under 1 second.

Our 777-300 was maintaining exactly 30,000 ft. at a heading of approximately 350, and the 340 was still climbing out of Tehran, passing just below us to the port side. We were absolutely less than a half mile laterally, and aircraft had climbed through our altitude and up to 32,000 by the time I located it on flightradar24 at a heading of 175. I'm guessing it crossed through our cruise at 30k within 5 seconds. Yes, the 340 is a very large aircraft and distances can be difficult to gauge, but I'd give the distance about "5 gates' worth" if parked at most terminals. I'd give the distance at around 1,500 feet laterally and maybe 800 below us. As our headings (in the opposite direction) were not quite parallel, and since W563 was still climbing, it seems this left an incredibly slim window for evasive maneuvering. A little more lift for the A340 or 2-3 degrees to the left for our 777 would have seen us uncomfortably close.

I know folks post about "near misses" all the time, and I'm absolutely not calling this a near miss, because it wasn't. However, in the roughly 1.5M miles I've flown, this pass was incomparably closer than I've ever seen at cruise, which is why I ask about spacing standards out of my own curiosity.

Interestingly, this particular aircraft (EP-MMQ) was the one that Iran abruptly diverted to Kish last December, so Tehran could prevent the wife and daughter of Iranian footballer Ali Daei from leaving the country, due to his support for anti-government rallies.