Draken International did buy approx. 25 ex-Polish MIG-21Bis a few years ago. Since then they’re remained in storage & Draken has indicated they will remain so for the foreseeable future. This primarily due to them having a quite short endurance & limited modern avionics eg radar, cockpit ECM etc. The Pakistani Mirages are also starting to get quite long in the tooth & would require a bit on an upgrade to bring them up to standard I imagine. The main reason why this Red Air seems to be taking off is due to the cost of utilising USAF/USN assets as adversaries. Apparently F16/F18/F15 cost so much per flight hour that this is why the services are turning to contractors. This is also why most of the contractors, bar Top Aces (Discovery Air Services), aren’t looking at used F16’s. It seems as though the services have specified a basic level of equipment they want provided, a supersonic fighter with 1-2 hour endurance, 4th Gen avionics with BVR capable radar, HUD, HOTAS, MFD & MILSTD 1553 as a nice to have. Cheers