when you go to end a flight it should give you the option to save the replay. I dont know how the current "Instant Replay" feature works although it cant work the way I want it. Otherwise there'd be replays online. It only has to record input from the user, and seeing how most aircrafts are on autopilot a lot of the time it wouldn't make the file sizes really large.

The reason I think this would be a useful addition to the community, is that good pilots could upload them taking off at such and such an airport in bad weather and landing safely in a destination. It could be an opportunity for novice pilots to see how to fly a plane properly. I think so anyway.

Well, unfortunately when watching a replay AI don't work. We should have added that to our loooong thread of FS2004 wishes, maybe MS can see it and make it better. Anyways, you can't save "replays" by making a flight video. Under options there is Flight Video. Click there and then click make video or add clip or something like that.

FS2002's replays are a little weird. They're based on the configuration of the aircraft at whatever point you request the replay - hence the static props if you've turned the engines off before doing so.