I have been getting into XP and wanted to know what programs for AI traffic are available that it's similar to what Alpha India Group has for P3D either freeware or payware. I know of a couple of addons/plugins but don't know which one is better.

I use Traffic Global in XP11. Pretty happy with it, except when I arrive at the destination airport, the gates are 98% full. If you want crowded skies, that will be a scenario. Less crowded skies - more free gates. JustFlight needs to tune that, but it's been like that from the start, so I guess it's not possible or not needed. Not sure how it works in XP12 though, others can share their experiences.

I only use the freeware XP12 PlugIn LIVE TRAFFIC which does two things it connects to a variety of online real time world air traffic sites such as Open Sky Network and the ADSB Radar Exchange Global Radar. It requires you download and install a large AI model library they recommend the BlueBell AI Library. It then takes the real world traffic data and generates the AI traffic in real time. Downside a bit fiddly to get a connection going and the OpenSky Network is free for a little while but then you have to subscribe - it is a minor $5 a month so more than happy with that. 

Gives great real time traffic and accurate aircraft types - not always the correct airline colours etc but good enough. 

Main downside the traffic generated in the sim is doing its real world thing so you can get run over or in the road on busy taxiways. A minor inconvienance. You can just go plane spotting sometimes at some locations. Oh and yes it gives airport and enroute traffic (high level stuff you will see contrails) so if you have something like Navigraph set up for a sim connection you can actually see that generated traffic on the Navigraph map interface. 

Proof of concept - this is me in the sim in the Shensee B707 in the queue for departure at Sydney Australia all the other aircraft are being generated by LiveTraffic. It gets quite busy. 

For me in out of the way places there is no traffic because there is no traffic!

Enroute high level traffic contrails being generated to the left of me:

 

LiveTraffic here, currently testing the feed from ADS-B Exchange which seems to provide more GA aircraft than OpenSkyNetwork.

The lack of ATC comms from the traffic can be compensated with X-ATC-Chatter, which also brings a very good ATC client for the user aircraft to the table.

I’ve installed LiveTraffic and so far it is working as intended. Although the AI sometimes behave in a weird way, moving back and forth over a Rwy, it gets the job done.

I tried all the traffic plugin and finally settled for World Traffic 3.  I found it has edge over all the others incluidng

• performance
• Real world schedule
• texture quality of AI aircraft
• ability to control parking spots 
• ability to control airport operations
• multi runway operations

Only thing that is flaky is TCAS. It works most of the time but doesn't work all the time.