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Comment by DebtDeflation | Hacker News Reader

If a plane is in the air, and can't get permission to land anywhere, well, they only have a finite amount of fuel onboard.

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A pilot WILL land, even without clearance. They're not going to crash their own plane. Either way, ATC has fallback procedures and can just use radio to communicate and manage everything manually. Get all the planes on the ground in safe order and then wait for a fix before clearing new takeoffs. https://aviation.stackexchange.com/questions/43379/is-there-...

Planes always get landing clearance via radio. "Planes in the air were unable to get clearance to land or divert" strongly suggests that the radios themselves were not working if it's actually true.

And if they can’t get it via radio they are trained to get clearance via visual sight with someone on the ground.

In the case of an emergency (which low fuel most definitely is) the captain has the ultimate authority and can tell ATC "I'm landing anyway".

That might be fine for a single or a few planes. But given the magnitude of the outage, what if a single airport had dozens of planes landing anyway.

There's a very good reason airport traffic control exists.

I'd be highly surprised if ATC systems were affected by this, but if anyone wants to correct me please do.

I wouldn't expect emergency rooms and 911 to stop working either, but here we are, so until someone says otherwise, I'm assuming some ATCs went down too.

I imagine the flight planning software they use was affected (so their ability to coordinate with other airport's ATC), but not their radio systems or aircraft radar (nearly all radar systems I've worked with are run on Linux, and are hardened to the Nth degree). Been out of the game for 12 years though, so things have likely changed.

The Tenerife disaster (second-deadliest aviation incident in history, after 9/11) was ultimately caused by chaotic conditions due to too many airplanes having to be diverted and land at an alternate airport that wasn't equipped to handle them comfortably.

I'd argue that Tenerife was due to taking off (in bad weather), not landing. But of course, a bunch of planes landing at the same airport without ATC sounds quite dangerous.

There were a lot of contributing causes, but it wouldn't have happened if not for the fact that Tenerife North airport was massively overcrowded due to Gran Canaria airport being suddenly closed (for unrelated reasons) and flights forced to divert.

The issue wasn't with landing specifically; I'm just using it as a general example of issues caused by havoc situations in aviation.

Also lack of visibility. The two pilots couldn't see each other through the fog.

Pilots know where there are other places to land, e.g. there are a lot of military strips and private airfields where some craft can land, depending on size.

I would expect this to affect airlines services, e.g. for check-in and boarding. I would be very surprised if this outtage affects ATC systems.

They would use those 4 magic words in aviation: "I'm declaring an emergency"

Obviously, they're going to land planes before they run out of fuel.

Or shortly after

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