I can also reciprocate that for me, this issue wasn’t present in the first flight or two in SU3, it started later. This really makes we wonder if there’s something user-side we can discover that helps.
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Can confirm this is also occurring in SU3 on Xbox X. Completed 5 airliners flights since SU3 installed. Every single one ends in a stutter/momentary freeze fest from final approach until parked at the gate. Even once at the gate, after engine shutdown and turning the avionics off, airport and aircraft textures struggle to render as the Xbox has maxed out its VRAM due to the mainthread loading up and never recovering.
I may have some good news to report here. Yesterday I decided to cleanup my graphics drivers so I ran DDU to perform a clean uninstall and re-installed. Adrenaline 25.8.1. After 3 flights I’m no longer seeing the MainThread increase. In fact its behaving as expected meaning higher values while at the airport/cities and falls while over unpopulated areas. I started my current flight in the Beechcraft G36 at LAX at around 22 ms and now over the desert I’m at 15 ms.
The controls menu issue is still present but the long flight issue seems to have been resolved for me. I will try with other aircraft but I wanted to let you all know what I found if you’re interested in giving it a try.
Update: Just tried one more flight Montreal to Toronto Boeing 737 Max. Left Montreal MainThread 22 ms arrived in Toronto 22ms. Little over 1 hour and maintain 60 fps for entire flight with a smooth landing. 
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Forst flight is most of the time always great, but do the same flight but the return flight also without reloading sim.
Maybe you had another problem, but this topic was created by me mainly, because, mainthread increases over time (2-3) legs in a row without reloading msfs.
I never had a problem with just one flight, but with the ones thereafter.
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Ok, I’ll try that, but the MTL to TO flight was part of the same session when I flew out and back of LA for over an hr. I just change planes and location but I’ll test it your way as well.
Tks
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Today I installed msfs2020 again with all addons and it is amazing how great it is running.
Though, I’m off of msfs24 for now and will monitor what happens with 24.
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Also have this problem. Sim works great on load, 100-110 FPS, after an hour and one sector done, only 65-70 frames, doesn’t recover.
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Did you vote, that they see a fix should be their priority?!
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@everybody please upvote this topic!
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same issue. Just voted. Hope they will fix it soon!
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I have shared the link to this thread on all my discord servers.
They are just sitting and reading all this without taking any action. This needs to be fixed ASAP!
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I’m afraid the problem doesn’t just show up on longer or multiple legs. I flew a short leg from BOS to IAD on a freshly rebooted system.
At departure in BOS, the main thread was sitting around 9.5 ms, but by the time I landed in IAD it had climbed to between 20 ms and 25 ms. On top of that, whenever I used the drone camera, something was hammering the main thread, causing spikes and massive stuttering.
After rebooting the PC and respawning at IAD under the exact same conditions:
Main thread was back down at 9–10 ms and no more spikes.
(9800X3D, 7900XTX, iFly 737-8)
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Today I tried also a short route from Frankfurt EDDF to Hamburg EDDH….after arrival main thread was sitting at 30 ms. After restarting the sim at the exact same gate main thread was around 20 ms.
Really shocking that such a cruical performance bug made it into the final release SU3 that cannot be avoided or rolled back to the good performing SU2.
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Agreed. Flew from LGW to AMS, an hour flight, performance great on departure by the time I got to the turnaround in AMS my FPS was halfed. Same happened on the previous flight after a restart between two different airports.
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Ok, so I just finish testing again. I used your test from Frankfurt to Hamburg and these were the results. I flew the Beechcraft G36 at 4000 ft.
Departed Frankfurt at 12:06. MainThread at 23ms
Over Wunstorf at 13:00. 13ms
Arrived at Hamburg at 13:35. 16.4ms
Then started my return trip at 13:40. Just after take-off it peaked just over 20ms but then settled back down to just under 15ms
14:10 back over Wunstorf on return. 13.2ms
Landed back at Frankfurt at 15:10. 24.7 ms
So as you can see, the clean un-install and re-install of my Adrenaline drivers seems to have fixed the issue for me. I can’t explain why but my MainThread issue during flight no longer exists.
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same issue here, did a rotation EDDP to EDDF and then to East Midlands in the 77L, the first flight was fine in performance but the second one was much worse in performance only explainable by this bug
Which adrenaline driver are you on? Since this topic is bug logged, it should not have anything to do with a clean driver Installation. Maybe it is a side effect. I don’t know? Did you use DDU in safe mode?
What is you driver you have installed ? NVIDIA ?
He said Adrenaline!
I dont know what Adrenaline is…