We currently offer a massive range of downloads for FSX, as well as older flight simulator add-ons for the ever-popular FS2004, FS2002, CFS3 and now becoming ever popular with dediced virtual aviators is Laminar Research's X-Plane series.
You have read the documentation of FSX of course, haven't you? And read about the Tower View Option. Ah, you missed that? Oops. Well, have a look at Mike Singer's blog, where he explains how you can not only use the Tower View in multiplayer (and see other planes) but how it is ALSO possible to use it in Free Flight mode and see AI traffic. Mike's blog is right here !