My memory isn't that good as it used to be, but I think anels9 is correct. At some point DSB/IRIS released several of the older models as freeware. I think the Mig-27 was one of them.
The links were available at the IRIS web-site, however the models were physically hosted at JayKay's site.
Since JayKey's site is gone, I think the models might be as well...............
Cheers,
Huub
However its labelled as "FSX/P3D", but looking at the history of this model, it might work in FS2004 as well.
b