There was some discussion in other thread recently that you can read here.
It’s hard to narrow it down to platform, and keep in mind these numbers likely include Gamepass users, but you can get a rough idea of numbers based on the information we have available.
2,000,000 “pilots”, which I would have to assume is unique players (on PC only, as the console version was not yet released), in the first 3 months of launch. Two weeks ago during an interview with HeliSimmer, Jorg said:
“This year, right this moment, I think we have four times the audience then when we launched”.
What exactly that means is up to how you interpret that quote, I suppose. Steamcharts estimates between 500,000 and 1,000,000 owners on Steam, where Gamepass is not available. I can’t find any info that might suggest how the rest of the playerbase is split.
Found this info regarding prerelease market research.
Ahead of its release, data firm Jon Peddie Research said that Microsoft Flight Simulator was going to result in $2.6 billion being spent on PC hardware and various peripherals. Interestingly, this was based on a forecast of 2.27 million copies of the game being sold within three years of launch. Safe to say that Microsoft Flight Simulator will likely reach this sales milestone within a fraction of that timeframe.
Those predictions seem to be based off copies sold so I don’t know how Gamepass plays into that, but the sim seems to be doing much better than anticipated overall.