Air Force acquisition executive Sue Payton stepped down from her position last week, Inside the Air Force has learned. Payton -- who has served as the Air Force's acquisition executive since August 2006 -- left the post on April 8, according to service officials. Her deputy -- David Van Buren -- has been appointed acting assistant secretary of the Air Force for acquisition. In a Jan. 23 letter to her acquisition corps, Payton said she would remain in her position...