The Defense Department's most recent F-35 concurrency estimate projects it will spend $1.76 billion to retrofit early Joint Strike Fighter production lots with new capabilities -- a slight increase from last year's $1.69 billion estimate. The Defense Department submits an annual report to Congress on its known and projected concurrency costs through the end of the development phase. Between 2012 and 2014, expected costs dropped by nearly $1 billion, but in 2015, the program started a slow, upward creep. The...