They have to be the simpler kind of models from the original FSX, circa 2006. Not very many legacy aircraft can be successfully converted for MSFS. If you want to learn how to generate custom AI traffic in MSFS, then have a look at my Youtube video I created it in order to introduce some militery AI aircraft into the sim and it behaves very well as traffic.

Unzip the download file and place the 4 folders into the Community folder, then you are good to go. When starting on a 9000 foot runway, allow the engines to spool up for 90 seconds, then gradually increase the throttle to full power and release the brakes. You have to guesstimate your speed and height. It does fly and responds to the normal control inputs and the cockpit detail is visible, but the instruments and MFD's do not work. This aircraft is a conversion of the original FSX FA-18 Hornet using MSFS Legacy Converter.