We were very saddened to hear that aviation pioneer and former NASA test pilot William H. Dana passed away yesterday. Bill was a legendary test pilot for many trailblazing programs, including one of our favorites, the X-15 suborbital spaceplane. SpaceShipTwo owes a great deal to the X-15 program, and to the men and women who built and flew that vehicle. Our thoughts are with all of those who knew and loved him.