Curious myself I looked at the GAS website
https://goldenagesimulations.com/ and did not see it listed. But I when I went to PC aviator I do see it listed (on sale for 12.48USD), I wonder if its been dropped.
I think the answer may be at the top of the GAS product page: planes for FSX, FXSE, and P3D; no mention of FS9.
There's a few other GAS planes, like the Boeing Model 40, which I have but which are no longer listed on the GAS product page.
One example is the GAS Boeing B-75. Another is the GAS Classic Waco Collection. Or at least those are the names on the installers.
I don't have either of these installed in FSX or P3Dv4, and I suspect that's because these planes were straight FS9 portovers to
FSX, with all the usual problems (nearby propellers disappearing behind far away clouds, windshields going opaque in the rain, etc.).
I didn't notice any of these problems in the Model 40 (although I didn't fly in the rain), which is probably why I still have it installed.
I also seem to recall (but I might be wrong) Paul from GAS saying awhile back that they were no longer going to offer certain older
planes, because these planes no longer measured up to GAS's current standards.
-RobM