The SR-71 spyplane required 85% Titanium construction. The CIA created several coverup companies which were used to purchase the titanium from the Soviet Union. Ironically, which was then used in turn to spy on them.
I used to work for a guy who was in the military and was stationed for a while on an airbase where these beasts flew from. He told me they fuelled them up with as little fuel as possible, because they leaked it all over the tarmac - they only didn't leak when they got in the air and the titanium heated up to working temperature. The planes literally didn't fit together properly until their titanium skins got hot from air friction. They'd take off , and then re-fuel in-flight as soon as possible.