I you fly an aircraft with a HUD it usally has what some people call a "birdie" or flight path marker. It basically shows you where you are going relative to the ground. The cool thing about it is that the difference between the birdie and the pitch attitude is almost equal to your angle of attack. So by looking through your HUD you know where you are going and at the same time you know your angle of attack. You can fly an approach just by looking at these two symbols. Great stuff! Every aircraft should have a HUD!