REX Atmos: the pictures are gorgeous, the software is miserable

Read enough reviews of REX Atmos and you notice they are all the same review. The pictures are gorgeous. The software is miserable. Nobody disagrees with either half.

FSElite gave it Editor's Choice on 13 October 2024 and spent most of the piece explaining that the marketing's promise of something simple and easy to use "also really isn't". On Contrail, where 55 people have rated it, the four written reviews average two stars and every one of them opens by praising the visuals before taking the interface apart. The most-liked, from 7 December 2024, ends: "hold on to your money." The most recent, from 28 March 2026, calls the interface "outrageously bad, almost maliciously so… a barely functional UI that looks like it was cobbled together overnight by their intern". Both of those are two-star reviews that also say the product does something close to essential.

Here is the part only aggregation shows you. We reviewed the successor, REX Atmos CORE for MSFS 2024, earlier today. The complaints are identical — sliders whose usable range is a few per cent of their travel, presets that must be reloaded by hand every time the weather or the light changes, no documentation worth the name. REX rebuilt this product from the ground up for a new simulator and shipped the same interface faults two years later.

And REX now calls this one Atmos Legacy. Their own site does, and so does Contrail. simMarket still sells it as "REX ATMOS MSFS20" with no hint of that, at €13.02, while the successor sits on the same shop at €12.41. On REX's own store both cost exactly $14.50.

We read eleven sources for this review: three store listings and every review text on two of them, the developer's product page, store and news archive, a full written review, three AVSIM threads running from January 2025 to 3 August 2026, a 52,000-view video review, and our own reading of the successor for comparison.

What you are actually buying

A separate Windows application that hooks the running simulator and changes how the sky is rendered, in real time, while you watch.

Price	$14.50 direct · €13.02 simMarket · $15.47 Contrail
Simulator	MSFS 2020 only
Current version	7.4.2025.0603 — a June 2025 build
Listed since	1 October 2024
Size	112 MB download, 187 MB installed
Developer's own name for it	Atmos Legacy
Upgrade path	Owning it gets you 50% off Atmos CORE for MSFS 2024

What it changes: an ozone function and true Rayleigh scattering for the sky's colour and light; a Visual Cloud Enhancement pass that fixes MSFS 2020's notorious "ash clouds", the dark grey mush the simulator renders where cumulus should be; ambient light and colour across the whole environment from ground to sky. You can build your own themes, save them, and publish them to a shared community library, or pull down other people's.

Three things it deliberately does not do. It does not touch your simulator's files — everything is applied in memory and reverted on exit. It does not change the cockpit interior, so your instruments stay readable. And it does not supply weather: it renders whatever Asobo Live Weather, ActiveSky, REX Weather Force or a saved preset is already giving you.

The obvious question, and the record answers it plainly. GSalden, on AVSIM on 27 January 2025, posted his Atmos preset next to a stock MSFS 2024 screenshot and wrote five words: "MSFS 2024 has it right out of the box…". This product exists to make MSFS 2020 look like the simulator that replaced it.

What the community consistently praises

The ash-cloud fix, which is the reason anyone tolerates the rest. REX's own before-and-after — the same valley under the same weather, muddy grey on the left and bright cumulus on the right — is an honest illustration for once. Skybreaker, giving it two stars on Contrail in March 2026, still wrote that what it does is "almost essential for 2020 at least, especially if you're flying in any non-cold and dry climate". That is the shape of the consensus: people who dislike the software will not uninstall it.

Second, the visual result more broadly. Easyjetsimpilot's full review — 52,000 views, October 2024 — is titled "Most Realistic Addon for MSFS 2020". Elmar Wegerle, three stars on Contrail on 19 December 2024: "Marvelous graphics, really outstanding… I would buy it again, just for the great immersion you get from it." Every simMarket reviewer says a version of the same thing.

Third, it costs nothing in frames. FSElite detected no performance impact. History, on AVSIM, put it as "no or very little impact on the FPS". For a real-time renderer hooking the sim, that is worth stating.

Fourth, the compatibility claim is real. It sits happily alongside ActiveSky, REX Weather Force, Asobo Live Weather, saved and imported presets, ReShade and Nvidia filters, on DX11 and DX12, and it leaves the cockpit alone. Nobody in the record reports a conflict with another weather product.

Fifth — and this is the one that deserves proper credit — REX fixed the biggest complaint. The December 2024 reviews all raged that your favourite preset would not load by itself and the application would not start with the simulator. By April 2025 that was done. V1ROTA7E, an AVSIM member whose signature lists 747, 757/767 and current 777 command, opened a thread with it: "They added an auto load feature so you can just start it up and it'll load your favorite presets automatically. My (and others) biggest gripe with the program was that you had to fiddle with the settings every time you restarted the sim or program. This makes it so much easier to use."

And sixth, REX went looking for the crash reports. When users raised CTDs on AVSIM on 22 April 2025, another poster produced a developer message from the REX Discord recruiting beta testers specifically for it: "We need your help to beta test REX Atmos 2020. If you've been experiencing CTDs (crashes to desktop), your feedback is crucial."

What keeps coming up as a problem

The interface — still open, and it is the whole complaint

There is no dressing this up. It is the most consistently condemned interface of anything we have reviewed.

joby33y, AVSIM, April 2025: "It's by far the most annoying, un-user friendly UI of any add on I've ever used." Skybreaker, Contrail, 28 March 2026: "outrageously bad, almost maliciously so, with poor user feedback, confusing and unexplained options, as well as bad search and save options."

The specifics, from the two most detailed Contrail reviews:

• You cannot keep a preset you like unless it is popular. "Not one of the top 5? Well too bad, you can't save it. You need to look it up every single time." (7 December 2024)
• Nothing tells you which preset is active. "There's no indication if a preset is currently active or not." (4 March 2025)
• The community library is unusable at scale. No rating system, so "it's all completely trial and error"; and the list is "full of duplicates (some with errors)". Even V1ROTA7E, writing to recommend the product, called sifting through the community combinations "a bit annoying".
• No minimise to tray, so it sits in your taskbar for the whole flight.

FSElite adds the mechanical faults: the Cloud Enhancement slider does nothing across its first half and then jumps, over-adjustment produces grainy morphing clouds and odd reflections, and Ambient Light settings can go "seriously strange".

Presets are static, so you tune the same flight twice — still open

This is the fault that survived into the successor. FSElite's finding in October 2024: settings optimised for the conditions you took off in stop working as the weather and the light change, so you "tweak everything all over again" mid-flight. Threshold found exactly the same thing about Atmos CORE on 2 February 2026, sixteen months later and on a different simulator.

The auto-load fix of April 2025 solved loading a preset automatically. It did not make the preset respond to anything.

Crashes to desktop — acknowledged, chased, never publicly closed

Benbo, AVSIM, 22 April 2025: "Causes CTD for some users, me being one of them, i tend to give it a wide berth if i want to be free of issues." REX opened a public beta to hunt it the same month. We could find no announcement that it was resolved, and the last build of this product is dated June 2025.

It has stopped moving — still open

Version 7.4.2025.0603 is fourteen months old. Skybreaker's March 2026 verdict opens "Seemingly abandoned in a not great state." A user posting on AVSIM on 3 August 2026 — sixteen days ago — reported that after installing it the text does not fit inside the window: "Letters are TOO big and not everything is visible without being able to scroll ??? What can I do?" No one has answered him.

None of that is surprising for a product its developer has renamed Legacy. It is worth knowing before you pay full price for it.

Being sold a successor while the current one was unfinished

One Contrail reviewer's complaint on 4 March 2025 has aged into something pointed. Noting that REX was already discussing upgrade pricing for the MSFS 2024 version, he wrote: "In my opinion, this is just greedy when the existing application isn't even a polished product." Atmos CORE duly launched on 21 August 2025 with a 50% discount for Atmos owners — and, per our review of it, with the same slider and preset problems intact.

Performance and stability

Two different answers, and both matter.

Frame rate: no cost, confirmed independently by FSElite in October 2024 and by AVSIM users. This is a colour and lighting pass, not a simulation, and it behaves like one.

Reliability: less settled. The CTD reports of April 2025 were real enough for REX to recruit beta testers over them, and the thread contains a user who abandoned the product to stay stable. Against that, most owners report no crashes at all, and the two-star reviewers complain about the interface rather than about stability — people do not write "hold on to your money" about software that keeps crashing; they write it about software that works and is horrible to operate.

The current build being fourteen months old cuts both ways. Nothing new has broken. Nothing has been fixed either, including a window-scaling fault reported this month.

Who should buy it

If you fly MSFS 2020 and the ash clouds bother you: buy it. That is the whole case and it is a good one. Nothing else fixes the grey-mush cumulus, the two-star reviewers concede the point, and at $14.50 with no frame cost it is the cheapest large visual upgrade available to that simulator.

If you fly MSFS 2020 in VR: buy it. joby33y, who called this the worst interface he has ever used, keeps it anyway because "it's the only way to filter / adjust overexposed skys while in VR, with changes on the fly". No filter or Nvidia setting does that live.

If you already own it and are moving to MSFS 2024: claim the 50% discount on Atmos CORE, but read our review of that first — the visual gain carries across and so do the interface faults.

If you have moved to MSFS 2024: do not buy this. It does not run there, and the successor exists. More to the point, an AVSIM poster comparing his tuned Atmos preset against stock MSFS 2024 concluded the newer simulator "has it right out of the box".

If you want to set something once and forget it: do not buy this. Presets load automatically now but they do not adapt, so a configuration that looks right at dawn will not at noon. Every reviewer who wanted set-and-forget ended up disappointed, in both this product and its successor.

If a bad interface will spoil it for you: do not buy this. Read the two-star Contrail reviews before you spend anything. They are written by people who like what the software does, which makes them the most reliable warning available.

If you are hunting a crash: uninstall it first. It is one of the add-ons that has genuinely caused CTDs for some users, REX ran a beta programme to find out why, and there is no public all-clear.

Where it stands today

REX Atmos is a good idea, executed beautifully in the only place that gets photographed and badly everywhere a person has to touch it. That combination has produced the most consistent review record we have encountered: five stars for the sky, two for the software, from the same people in the same paragraph.

The store numbers show how much the sample matters. simMarket has ten reviews and displays a flat 5. Contrail has 55 votes and shows 3.87, with every written one of them a complaint about usability. The larger, more recent sample is the one to trust — and notably, Contrail rates the MSFS 2024 successor slightly higher, at 4.14.

What has changed since the reviews that shaped its reputation is worth saying clearly, because REX gets little credit for it: the auto-load feature landed in April 2025 and removed the single biggest daily irritation, and the company went publicly looking for the crash reports rather than ignoring them. What has not changed is everything else, and the last build is from June 2025 on a product now officially named Legacy.

Our 3.6 is a wide spread — 4.2 for what it renders against 2.2 for the thing you operate — and it should be read as a recommendation with a warning attached rather than a hedge. If you are still flying MSFS 2020, buy it, spend one evening finding a preset you like, and then try never to open the window again. That is genuinely the best way to own this software, and it is a strange thing to have to write about a product whose entire purpose is letting you adjust things.