Originally Posted by
sandiego89
It is perhaps worth mentioning that while the airframes were smaller than something XB-70 sized, OXCART, Have Blue, Bird Of Prey, Tacit Blue, Senior Trend, various MiG's, various helos, some very large and complex space based sensors, and now a 6th gen fighter jet were all flown in secrecy by the USA and some of these were large and complex programs. OXCART was over 100,000 pounds, quite complex and 15 were built. Not a small program.
All those programs are now in the public domain, most have been for decades, and many of the airframes are in museums. If you want to know how to build a Mach 3+ aircraft, not only is there plenty of information to get you started on Wikipedia, but at least one museum has a pair of J58 engines outside the airframe that you can photograph and measure to your heart's content. Some of these aircraft did some pretty provocative things back in the day, but you can read all about it in Ben Rich's autobiography and watch interviews with the aircrew on YouTube.
In that context, why would another program from the same era, that was also retired due to cost/obsolescence, and who's successor is very much in the public domain, still be under wraps?
For the answer to that question have a look at the two links posted by ORAC, the first of which is a particularly good read.