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As of the early 2000s, ATC was still using vacuum tubes. In fact, the FAA was the single biggest buyer of vacuum tubes in the world at the time, almost all of them sourced from former Soviet bloc countries. I think they've all been replaced by now, but I can't say that with 100% certainty.





They might still be - aside from guitar amps, vacuum tubes' biggest relative strength was in high power radio amplification.

Which is what baffles me about the current situation and gives me a lot of hope for this effort. We should've been updating this stuff in the 90s, but successive administrations of both parties have just passed the ball on this one.

I see this the opposite way: kudos to the FAA for sticking it out so long on legacy hardware and software as long as they have!

ATC is a safety-critical function that has what amounts to a 100% uptime requirement. Whatever system they're running currently either works or has known flaws that they know how to work around, and air traffic controllers have been trained on these systems for more than a generation now. Upgrading merely for the sake of being up to date would have been foolish no matter how much funding Congress would have given them.

If they're saying that they need the upgrade now, I'll trust them on that, but it was the right call to make it last.


> ATC is a safety-critical function that has what amounts to a 100% uptime requirement. Whatever system they're running currently either works or has known flaws that they know how to work around, and air traffic controllers have been trained on these systems for more than a generation now.

The problem is that Eurocontrol (for example) has modernized their systems without much fuss, and UK NATS even has remote tower ATC now (https://www.youtube.com/video/Ii_Gz1WbBGA). It seems that FAA is stuck in the past, not just using old systems because it's reliable.

> Upgrading merely for the sake of being up to date would have been foolish no matter how much funding Congress would have given them.

I would agree if the system is still fit and proper, but even in 2005 the ATC systems in the US is not really fit and proper that there has been multiple plans to rehaul the system. It is really miraculous that the only system failure happened in 2023 (NOTAM offline), but that's due to tireless dedication that's certainly burning unneded manpower.

Unlike in Europe where civil servants have the sway to just do it, it seems that the US is an expert in political bickering on things that aren't really political.


My understanding is that remote tower ATC is something that had to happen at that airport due to geographic constraints rather than some kind of next step for ATC in general. Given a choice between being able to physically look out the window and not, from what I understand being able to see out is always preferable.

The rest I don't know enough to comment on, so I'll assume you're correct.


> ATC is a safety-critical function that has what amounts to a 100% uptime requirement. Whatever system they're running currently either works or has known flaws that they know how to work around, and air traffic controllers have been trained on these systems for more than a generation now. Upgrading merely for the sake of being up to date would have been foolish no matter how much funding Congress would have given them.

I do not have enough knowledge to disagree on this. But I will say the FAA is still on floppy disks when the US Nuclear Arsenal moved off floppies back in 2019.

https://www.nytimes.com/2019/10/24/us/nuclear-weapons-floppy...

Yes, they have different requirements and yes, SACCS was using 8 inch IBM mainframe floppies from the 70s, but they are both 24/7 critical systems.

> If they're saying that they need the upgrade now, I'll trust them on that, but it was the right call to make it last.

The real answer is likely embarrassing incidents that came up during the start of this presidency. There is now political will to address it; instead of 'before' it becomes a problem. They are on Windows 95-it was budget issues.


> I do not have enough knowledge to disagree on this. But I will say the FAA is still on floppy disks when the US Nuclear Arsenal moved off floppies back in 2019.

Well this isn't very long in terms of overhauling safety-critical systems that have many decades worth of processes and infrastructure built up around them, is it?


> Well this isn't very long in terms of overhauling safety-critical systems that have many decades worth of processes and infrastructure built up around them, is it?

Do you actually know if 6 years is enough time? If so, provide info.

As for myself, I do not know. I do know once it was reported they were on floppy disks; they finished moving off it in 3 years. If wasn't for the media report I doubt it would happen. Once again, different systems, but likely public embarrassment motivated the move more than anything else.

https://www.npr.org/sections/thetwo-way/2016/05/26/479588478...


Upgrading merely for the sake of being up to date is essential if you want to retain the capability to upgrade at all. You have to exercise your upgrade muscles, otherwise they become weak and flabby. At some point you're so far behind that upgrading becomes nearly impossible, and then everything just collapses.

Er...they actually tried and failed.

"I stopped counting long ago, but there have been many, many attempts to try to modernize the US’s air traffic control (ATC) system over the years"

https://crankyflier.com/2025/05/12/the-us-government-tries-t...

I am sure you can find better sources as there are so many of them.


So floppy disks were still used in the 90s. Windows 95 obviously came out in the 90s. Perhaps they did update this stuff in the 90s?



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