Hi, I'm releasing a cross-platform multiplayer client for joining FSX (boxed), FSX:SE and Prepar3D (possibly X-Plane at some point).
Available here, http://pmem.uk/joinfs.
Here's a list of current features:
Pilots can join with different simulator versions FSX (Boxed), FSX:Steam, Prepar3D. (Possibly X-Plane in future).
Record aircraft and play back recordings live to other pilots in a network. Overdub new aircraft onto a recording.
Animations are transmitted over the network; landing gear, elevator, ailerons, rudder, propeller, canopy, lights and smoke.
Pilots can be present on virtual ATC networks at the same time as JoinFS. This means that all aircraft in the JoinFS network will be shown using smooth low-latency movement.
It's free to use (donation-ware).
Thanks,
Peter