Family poster of F-35 flight test fleet

CF-3, shown above in a radar cross section test chamber, is preparing for first flight later this month to fulfill a 4.5-year-long effort to redesign, build and fly 12 weight-optimized Lockheed Martin F-35 flight test aircraft.
It has been harder, more expensive and certainly more frustrating than anyone probably imagined on 6 December 2006, the day AA-1 first flew. That aircraft, designed to meet a discarded specification, has since been retired to live-fire testing.
The next test aircraft to achieve first flight was BF-1, which flew nearly three years ago on 11 June 2008. Another flight test aircraft, CF-4, was added to the test programme last year, but won't join the fleet for at least two years.
For now, these 12 aircraft represent the sum of an estimated $54.3 billion investment by the US Department of Defense (DoD) to complete a 7,500hr development test programme that now will stretch for 10 years, according to the DoD's latest selected acquisition report.