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Comment by antubbs | Hacker News Reader

Eh. e.g. the north atlantic tracks have been around since the 1960s. GPS wasn't available to the public until Korean Air Lines Flight 007 in the 1980s.

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The OP means that satnav ensures that two aircraft on a reciprocal or identical track will now pass over one another, whereas there used to be navigational slop that would give some unintentional but useful lateral displacement.

Ironic that you should use the term 'slop', since that's exactly how they avoid flying the same route across the Atlantic tracks for example (Strategic Lateral Offset Procedure).

Also worth noting for the transatlantic paths is the direction of traffic. When it's morning in North America, traffic is predominately westbound. When it's night, traffic is predominately eastbound.

Right now, it's the middle of the day (12:50p Central). There's a bit of a mix[1], but it's still predominately westbound.

The consequence of this is that most traffic will be separated by at least 2000 feet. Eastbound traffic will (generally) be at odd Flight Levels (so 29000 feet, 31000 feet, etc.) while Westbound traffic will be at even FLs (30000 feet, etc)[2]. This assumes RVSM airspace.

[1] I'm just looking at the transatlantic traffic on https://flightaware.com/live/

[2] https://www.law.cornell.edu/cfr/text/14/91.179

> until Korean Air Lines Flight 007 in the 1980s

Woah, the soviets shot down a Korean airliner with air-to-air missles killing 269 people? Never heard that story. Crazy.

https://www.wikiwand.com/en/Korean_Air_Lines_Flight_007

Yeah, that was definitely the #1 story in the news when it happened. Much like https://en.wikipedia.org/wiki/Iran_Air_Flight_655 there's no shortage of uncertainty around the real story.

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