I recently noticed an increasing amount of questions about Project AI heres some basic info for those curious about "PAI"

Project AI aircraft are decent quality aircraft (Not all have animated parts) but they are easier on your framerates than standard AI aircraft. The air and aircraft.cfg files are not all accurate, for instance, the default aircraft.cfg of the a 340 puts the engines at 12,000lbs of static thrust. Realisticly it is 31,200lbs (DO NOT CHANGE THIS UNLESS YOU CHANGE THE WEIGHT TO A REALISTIC LEVEL AS WELL OR YOUR AI AIRCRAFT WILL FLY LIKE FIGHTERS) some PAI airlines do not say the airline name (Instead of saying "Southwest 1123" a southwest jet says " 1123") PAI aircraft are well-painted (only a few minor flaws) and they fly the close-to-real airline flight plans. I reccomend upgrading to PAI if you want the most realism out of your game. 

Did I forget anything?

I think that pretty much covers it.

I would amend though, and say that I've got a huge PAI fleet, and I've never once noticed anything irregular, such as the speed of the A340.  That's not to say it isn't wrong, just that if it is, I've never noticed it to the point where it affected me.

It's a good quick way to build up your AI files...highly recommended.  (Also, use their Default AI traffic remover...get those Orbit's outta there!)