CSS 737's performance is the worst I've ever seen from an aircraft in MSFS 2024 so far. I'm averaging 16 fps without frame gen. For comparison, the second most heavy aircraft in terms of performance that I have, the FBW A380, I get 28 fps. The bizarre thing is that the aircraft loads with fps in the 20-25 fps range, which would be minimally tolerable with frame gen, but when I enter the route in the FMC, the performance inexplicably drops to 16 fps. Other people report performance drops when activating LNAV.

The worst part of the low performance is hearing from the developer there's no way to improve performance without rewriting the aircraft from scratch, which they don't intend to do. What I suspect is that the poor performance isn't due to the modeling or textures (which are subpar, to be honest, and shouldn't cause poor performance), but rather the module CSS uses to run systems outside the simulator, like the Fenix A320.

I believe CSS's implementation is different from Fenix's, which would explain why the performance drops simply when using the aircraft's systems. 16 fps is unacceptable performance in any context. There are aircraft with textures a thousand times better and with much more complex systems where I can achieve more than double that performance.

As if the poor performance wasn't enough, the aircraft has other fundamental problems: LNAV struggles to stay stable in a straight line, overshooting on every turn. VNAV can't hold altitude. Auto Throttle either works strangely or simply doesn't work at all. Other systems work in bizarre ways and the sounds are simply bad, even worse than default aircraft.

I think the only positive is that CSS offers an opportunity to fly the aircraft for a month for $5 before committing to buying it. I did 3 flights and already uninstalled it. This aircraft is far from being of acceptable quality, both in terms of performance and systems.

Edited June 10Jun 10 by edu2703

31 minutes ago, edu2703 said:

CSS 737's performance is the worst I've ever seen from an aircraft in MSFS 2024 so far. I'm averaging 16 fps without frame gen. For comparison, the second most heavy aircraft in terms of performance that I have, the FBW A380, I get 28 fps. The bizarre thing is that the aircraft loads with fps in the 20-25 fps range, which would be minimally tolerable with frame gen, but when I enter the route in the FMC, the performance inexplicably drops to 16 fps. Other people report performance drops when activating LNAV.

The worst part of the low performance is hearing from the developer there's no way to improve performance without rewriting the aircraft from scratch, which they don't intend to do. What I suspect is that the poor performance isn't due to the modeling or textures (which are subpar, to be honest, and shouldn't cause poor performance), but rather the module CSS uses to run systems outside the simulator, like the Fenix A320.

I believe CSS's implementation is different from Fenix's, which would explain why the performance drops simply when using the aircraft's systems. 16 fps is unacceptable performance in any context. There are aircraft with textures a thousand times better and with much more complex systems where I can achieve more than double that performance.

As if the poor performance wasn't enough, the aircraft has other fundamental problems: LNAV struggles to stay stable in a straight line, overshooting on every turn. VNAV can't hold altitude. Auto Throttle either works strangely or simply doesn't work at all. Other systems work in bizarre ways and the sounds are simply bad, even worse than default aircraft.

I think the only positive is that CSS offers an opportunity to fly the aircraft for a month for $5 before committing to buying it. I did 3 flights and already uninstalled it. This aircraft is far from being of acceptable quality, both in terms of performance and systems.

I understand how disappointed you are. What's your spec by the way, just for reference since I am kind of interested in paying for 5 dollar trial

Edited June 10Jun 10 by History

9 minutes ago, History said:

I understand how disappointed you are. What's your spec by the way, just for reference since I am kind of interested in paying for 5 dollar trial

RTX 5070

Ryzen 5 5600

32GB RAM

2 minutes ago, edu2703 said:

RTX 5070

Ryzen 5 5600

32GB RAM

Apart from your valid concerns on the CSS optimization, the CPU might be the bottleneck. But you are probably right, it shouldn't affect as significant as you have described. Ryzen 5 5600 is still OK, maybe similar to i5 12 or 13 series.

40 minutes ago, edu2703 said:

[... ]LNAV struggles to stay stable in a straight line, overshooting on every turn. VNAV can't hold altitude. Auto Throttle either works strangely or simply doesn't work at all. [...]

While alot of your complaints are valid, the LNAV/VNAV/AT have been pretty solid. I'm not saying this is you but a lot of complaints I've seen are people treating it like an NG, and the classics perform a little differently. If you're on the discord feel free to tell us exactly what's going on and hopefully can help sort out the issue.

FYI I am not a dev.

3 hours ago, edu2703 said:

CSS 737's performance is the worst I've ever seen from an aircraft in MSFS 2024 so far. I'm averaging 16 fps without frame gen. For comparison, the second most heavy aircraft in terms of performance that I have, the FBW A380, I get 28 fps. The bizarre thing is that the aircraft loads with fps in the 20-25 fps range, which would be minimally tolerable with frame gen, but when I enter the route in the FMC, the performance inexplicably drops to 16 fps. Other people report performance drops when activating LNAV.

The worst part of the low performance is hearing from the developer there's no way to improve performance without rewriting the aircraft from scratch, which they don't intend to do. What I suspect is that the poor performance isn't due to the modeling or textures (which are subpar, to be honest, and shouldn't cause poor performance), but rather the module CSS uses to run systems outside the simulator, like the Fenix A320.

I believe CSS's implementation is different from Fenix's, which would explain why the performance drops simply when using the aircraft's systems. 16 fps is unacceptable performance in any context. There are aircraft with textures a thousand times better and with much more complex systems where I can achieve more than double that performance.

As if the poor performance wasn't enough, the aircraft has other fundamental problems: LNAV struggles to stay stable in a straight line, overshooting on every turn. VNAV can't hold altitude. Auto Throttle either works strangely or simply doesn't work at all. Other systems work in bizarre ways and the sounds are simply bad, even worse than default aircraft.

I think the only positive is that CSS offers an opportunity to fly the aircraft for a month for $5 before committing to buying it. I did 3 flights and already uninstalled it. This aircraft is far from being of acceptable quality, both in terms of performance and systems.

Ouch!.....that's too bad. I was really looking forward to this one. I might try that $5 trial but I don't know if it's even worth it at this point.

On 6/7/2026 at 2:30 AM, sd_flyer said:

I wonder how could it interfere because of FFB. FFB merely mimic actual yoke movement in the cockpit

FFB stick and yokes don't automatically return to a neutral central position if the FFB is active and I've come across a few planes where the plane doesn't understand FFB thinks that's because the users is constantly moving the controls.

2 hours ago, Matchstick said:

FFB stick and yokes don't automatically return to a neutral central position if the FFB is active and I've come across a few planes where the plane doesn't understand FFB thinks that's because the users is constantly moving the controls.

That is how yoke act in real airplane. It return to what ever elevator trim adjusted to. I'm using Moza FFB and it to me it acts as real airplane. When use elevator trim FFB respond and move to position I trim to.

10 hours ago, sd_flyer said:

That is how yoke act in real airplane. It return to what ever elevator trim adjusted to. I'm using Moza FFB and it to me it acts as real airplane. When use elevator trim FFB respond and move to position I trim to.

And as I say, some planes don't like the yoke not returning to the centre position and have to have the FFB effects disabled to fly properly.

5 hours ago, Matchstick said:

And as I say, some planes don't like the yoke not returning to the centre position and have to have the FFB effects disabled to fly properly.

Resetting trim to neutral will move yoke to neutral position. Autopilot manipulate elevator trim and can easily adjust yoke position to whatever position required. If developer have issue with that they don't understand how control surfaces work. We all know when autopilot engaged yoke suppose to move on it's own to whatever position servoes + trim dictates.

Little glimpse into upcoming new sounds..

Hello, Captains!

Hope @everyone are all enjoying your flights with the CSS 737-300 and 737-400.

While our team is on a short break from development for some much needed rest, we'd like to share a very exciting preview from our partners at Immersive Audio - who are currently working on an all-new sound package for the CSS 737 Family, featuring significantly higher quality and fidelity, spatial audio and more!

This package will replace the current one as the new default soundset for the CSS 737, and all users will receive it as part of a free update!

Please note that this is an in-development preview, and as such, many things are not final and will be changed before release. However even at this stage, you can clearly hear the difference between the old soundset and the new one!

Enjoy, and stay tuned for more news!