I would like to know about the purpose of multiplayer function in FS 2004. Is that means 2 person flying together?THanks

Yes. 2 or more people can fly together, and normally will be able to see the other pilot in their own game. It can be a fun experience.Users with Routers and Firewalls will sometimes have difficulties, but normally these problems can be resolved by asking a few questions to the group.

Er, not quite.It means a number of you can fly together, in Fs2002 it was limited to 16, not sure what the limit is in FS2004.Having said that you all have to be able to link into the same 'game'.3 ways I can think of off the top of my head.Arrange with your mates a time and place to fly. Tell them your IP address. Start FS and 'host' a multiplayer session and then your mates can connect to your PC over the Internet and you can all fly together.Join the MS gaming Zone and join one of the hosted MP sessions.Join Vatsim or IVAO and fly over the Internet anywhere in the World and interact with real people acting as ATCs.All the above activities require the the FS Multiplayer function.