Blood, sweat and tears.
Seriously though, like Atreides says, 3DS max and either Photoshop, Paint Shop Pro or The Gimp will certainly get you a far way into building your own aircraft, mapping them and then skinning them. Be prepared for a long haul though, it can take a while depending on the complexity of the aircraft you may wish to build. In this case, the B-2 Spirit could be deceptively difficult. Although looking like a fairly simple airframe, I imagine trying to get the curve and flow of the fuselage just right would take a while. It could be worth trying to start off building very simple, low poly objects and airframes. In actual fact, building weapons starting off is a great stepping stone, they are more simple than aircraft and turn out to be a much smaller work load.
Once you're all modelled up with your aircraft comes the importing stage. This will include optionally building a correct pit for the bird and doing all the necessary ini creating to ensure your aircraft behaves and operates correctly in the game.
Have a look at TK's exporter notes and mustang's 3d modelling tutorials, they are goldust to any new modeller.