FighterControl

Im pretty sure the only way to play FS2004 online is via VATSIM or IVAO but Im not sure if there are any other ways, there more than likely is.

Zac

I think FS9 has its own Gameshite..sorry..spy lobby that you could use. Otherwise it's VATSIM or IVAO as Zac says.

Nothing wrong with Gamespy

you can play online using FSINN, alongside others using FSX. We use FSINN over at UKMIL

Download FsHostSpy: http://www.chocolatesoftware.com/fshostspy/" onclick="window.open(this.href);return false;

I used to use this program to find servers to fly on quite a while ago, Also you can host your own Server by using the FSHost program that's also linked on the page

Nothing wrong with Gamespy at all, Chris.
I have been disconnected twice since November and manage to do 2-3hr missions no problem. Using Teamspeak 3 for voice.
If you sit in the lobby or free flight you will no doubt get disconnected but if you use the "flight training" server then it is stable.
I cannot use FSInn or any of the others as they use Simconnect and mine is "broke".