How do you add AI aircraft? and How do I increase traffic when the traffic option is all the way up?

Best way to add AI aircraft would be to download utilities like AFCAD. It's available in the AVSIM forums.

To add your own AI you need two tools.One is AFCAD two which allows you to edit the airports to create more parking for the planes (it does far more but for adding AI that's the main part).Secondly is Ttools, which allows you to compile flightplans to tell the sim where to have aircraft fly to and from etc. Both of these tools are available on avsim.You can look for other person's files on avsim that add traffic. I have many available that add traffic to some airports in Southern Ontario Canada.For extensive airline traffic you have two main options. The best free option is the packages available from Project AI. You can check out their website at http://projectai.flight1.net . Their official files cover over 80 airlines. It comes with a self installer so it is very easy to install them.The second option is buying Ultimate Traffic. This will add something like over 300 airlines into flight sim as well as GA traffic with proper callsigns. This is a great option if you're willing to pay, nothing else compares. If you have a lower end system I wouldn't bother however as AI traffic does hit hard on the framerates.

3rd option would be http://www.mostrealisticai.com/Thats the best flightplans you can find, up to date winter schedules for real airliners you can use in conjunction with the PAI aircraft (or other such as FSP/Aardvark aircraft).They have a good installer for the flightplans as well.

I second the idea of the following 3:1) TTools2) www.projectai.com3) AFCAD files