@Ken: thank you. I had never seen those pictures. In his book, Ben Rich says that one D21 even flew up to Russia after signal was lost.

Which ‘inspired’ the Tupolev ‘Voron’ lookalike….. http://www.secretprojects.co.uk/forum/index.php?topic=2199.0

http://www.ansuitalia.it/Sito/Sezioni/Geopolitica/Lockheed_D-21_e_Voron/Voron_1.jpg

Ken