Moving the A-12 Blackbird
This
 is one you'll want to keep in your aviation archives  because it's 
exceptionally interesting and heretofore,    a virtually unknown story.
   
It gives you a small clue to how expensive just one phase of the program was and the measures taken to maintain its secrecy.
The secret convey that moved the A-12 (Pre SR71 Blackbird) from Burbank, CA to Area 51 for flight testing.