Hi
Minimum is:
CPU:2 GHz Quad Core
RAM: 2 GB
Video Card: DX 10 card with 1 GB VRAM (NVIDIA GeForce 8800 GT or ATI Radeon HD 2900 Pro)
To play it reasonably I would say some better i3 or any i5 CPU and decent graphic card (GTX 750 comes in mind)
Then again, I play on three years old laptop with old i7 and GTX 460M, almost all on high. This game is pretty cheap to run, methinks.
Also, some kind of HOTAS joystick comes in handy (X52pro). Later on, TrackIR is awesome if you can spare some 170 bucks. And of course reasonably big monitor or TV to really enjoy all the stellar awesomeness