Sim Updates in Microsoft Flight Simulator 2024, aka MSFS 2024, are the mechanism Asobo uses to deliver engine-level fixes, performance work, and simulator-wide features (separate from Marketplace aircraft/scenery updates). Sim Update 4, aka SU4, is being positioned as another stability, visuals and quality-of-life update — an important one because it targets persistent issues and adds refinements reported since launch and since Sim Update 3. The team is running SU4 as a public beta so players can test fixes across a huge variety of hardware, peripherals, and third-party add-ons before the changes are pushed to everyone.
How the public beta is progressing
- Public Beta start: Asobo announced the Sim Update 4 public beta on September 8, 2025 and made the first beta build (version 1.6.3.0) available across Steam, Windows PC and Xbox.
- Ongoing iterations: The team has pushed follow-up pre-release/beta builds (for example build 1.6.7.0 released in mid-September 2025) with incremental fixes and telemetry-driven changes. Asobo’s development updates explicitly ask testers to participate and file reports/surveys so the team can stabilize SU4.
Because these builds are still being iterated, the “full” public release date is deliberately fluid — Asobo is prioritizing stability and third-party compatibility rather than prematurely shipping a problematic update. The official channels have not announced a final release date at the time of writing.
What’s New & Improved in Public Beta 4
Below is a fairly comprehensive breakdown of changes documented in the SU4 beta release notes (especially version 1.6.7.0) and community-reported improvements. These cover rendering, stability, aircraft systems, SDK changes, and more.
Rendering, Lighting & Visual Effects
- Snow & rain illumination at night
One of the oft-cited visual bugs in earlier builds was that precipitation (snowflakes, rain) would not receive correct lighting at night, making them nearly invisible or unconvincing. Beta 4 fixes this, restoring more realistic appearance in nocturnal weather conditions. - Emissive material reset
In previous builds, surfaces with emissive (“self-illuminating”) materials sometimes “stuck” glowing even after lights were turned off. In Beta 4, that behavior has been corrected—emissive states reset properly when their associated lights are disabled. - “Blurry sepia night lighting” corrected
The dev notes mention that excessive bloom and sepia masking at night were being toned down. Cityscapes and surrounding terrain should appear darker and more natural under low light, without the artificial halo or washed sepia tint. - Instancing draw distance & renderer optimizations
In 1.6.7.0, the instancing draw distance (i.e. how far away repeated geometry is drawn) has been limited, with a minimum size now capped (0.25%). Also, renderer path optimizations aim to reduce rendering overhead, potentially improving framerate and consistency. - Terrain engine and general render performance
The update includes optimizations in the terrain engine to reduce stutters or load hitches, especially in densely textured areas or large elevation changes. - Grass rendering optimizations (in earlier beta builds)
In the initial 1.6.3.0 beta, Asobo’s notes mention an optimized grass rendering pipeline—likely to reduce the overhead of drawing millions of grass blades or patches when zoomed in or in low-altitude flight.
Stability, Load / Crash Handling & Performance
- Crash fixes on UI / periphery systems
- Fix for crash when repeatedly opening/closing the weather panel.
- Fix for crash when opening the Aircraft Capture Tool.
- Fix for infinite load conditions in certain states.
- Renderer and engine optimizations to reduce crashes and unresponsive states.
- Performance tuning of thread paths and input systems
Some of the SU4 betas target the main CPU thread and input systems—this helps reduce CPU bottlenecks in complex scenes (e.g. airports, dense traffic, heavy scenery). - General stability improvements across subsystems
Because flight simulators integrate dozens of complex systems (weather, traffic AI, physics, scenery, user input, etc.), SU4’s beta notes show many fixes across subsystems to reduce edge-case crashes and desync events. - Renderer & instancing culling fixes
Better culling (not drawing what’s off-screen or too small) helps reduce GPU/CPU load and prevent frame drops. The instancing draw distance limitation is part of this.
World, Traffic & Scenery Fixes
- City night lighting and ambient shading
As noted earlier, “blurry sepia” nighttime visuals are being corrected so city lighting appears more natural. - Road traffic on residential roads
A bug had been documented in which cars would not move along residential roads. This is now fixed. - SDK & WASM / API stability
The SU4 beta includes a significant number of fixes in the WebAssembly (WASM) API, WASI functions, and the Vars API for developers, reducing crashes or misbehavior in add-ons that leverage these systems.
Community-reported regressions & third-party compatibility issues
Public betas are valuable because they surface regressions tied to the vast third-party ecosystem. The community and add-on developers have reported a mix of improvements and new/remaining issues:
- Third-party add-on problems: Some users have reported incompatibilities with popular add-ons (for example GSX and certain airliners) after switching to the SU4 beta, often related to dataref or API changes that require third-party updates. These reports are being actively tracked in community forums.
- Mixed aircraft behavior: While some aircraft (including some PMDG titles) appear to load and run better for some users, others report crashes or freezes with certain heavy third-party aircraft — a classic symptom of API/SDK surface changes needing plugin updates. Community forums and threads show active testing and mixed results at present.
Asobo’s public communications explicitly invite third-party developers and testers into the beta so those compatibility problems can be discovered and (ideally) addressed before the global rollout.
What Asobo has said about release timing
As of the latest official development update, Asobo has not given a precise, final public release date for SU4; instead they are iterating on beta builds (e.g., 1.6.3.0 through 1.6.7.0) and asking beta participants to report issues and vote in forum surveys. That means:
- No firm wide-release date yet. The team’s priority is stabilization rather than announcing a date and risking a rushed rollout.
- Typical cadence: Historically, Microsoft/Asobo have run the public beta for a variable period (a few weeks), pushing multiple builds as fixes accumulate and regressions are handled. Once telemetry shows stability across broad hardware and third-party ecosystems, Asobo flips the switch to a general release. Comparing previous SU cycles gives a reasonable expectation of weeks, not months, but this is dependent on what the beta uncovers.
Realistic projection: If beta feedback is mostly positive and no critical regressions block major third-party flights, a general release often follows within a few weeks of the first public beta. If significant compatibility/regression issues are found, this window can lengthen. Because Asobo has already moved multiple beta builds in mid-September, a general release in late October 2025 would be reasonable if the beta stabilizes quickly — but this is a projection, not an official date.
How you can participate
If you want SU4 to be robust at full release, participating in the public beta is the fastest way to help:
- Join the public beta on PC (MS Store or Steam) or Xbox — Asobo published instructions with the SU4 beta announcement. Participation lets the dev team see telemetry from your hardware/peripherals and speeds up regression discovery & fixes.
- File detailed reports: Use the official forums and Asobo’s survey links after testing. Include hardware, OS, add-ons installed, and reproduction steps for crashes or odd behavior.
What to watch for in the next beta 4 builds
Based on official notes and community threads, the next iterations will likely focus on:
- Continued stability and crash fixes driven by telemetry.
- Third-party compatibility patches and possible refinements to SDK behavior if developers report breaking changes.
- Small visual regressions that beta testers find and the team addresses (e.g., lighting edge cases, LOD issues, or instrument rendering).
Bottom line — should you install the beta now?
- If you’re a casual simmer or prefer a stable experience: Wait for the public, full release. Betas are great for helping development but sometimes introduce temporary regressions with third-party content.
- If you like testing, troubleshooting, or you’re a developer: Join the beta, report issues, and help shape the release — especially important if you rely on third-party software (your reports help those developers prioritize fixes).
Final thoughts
Sim Update 4’s public beta (Beta 4) is the crucial middle ground between Asobo’s internal testing and a simulator-wide push. The beta already shows meaningful fixes (night weather illumination, emissive material behavior, localization fixes, UX touches and aircraft-specific corrections) and is being iterated quickly with multiple builds.
The final public release date is still unannounced — Asobo is clearly prioritizing stability and third-party compatibility over an arbitrary ship date, which is the right approach for a platform with a massive and diverse user and add-on base. Expect a full release once the team is confident telemetry + community testing show the update is stable across most configurations — historically that means a matter of weeks following the start of a public beta, provided no major regressions are found.