@Ryan Hanks: Sure, because everything out the window is more than a few dozen meters away (or so the pilots hope!) and accommodation for 50 meters to infinity is pretty close. but having your virtual image at infinity and your eyes focused at 3 feet leaves you with a blurry double hud image.

making AR "glasses" is not a matter of DARPA funding. It's a matter of the limitations of optics that focus the virtual image at the right place. You can't focus it both at 3 feet and 300 feet.