We had one SR-71 mission back in the early 80s on which the plane was flying south along the E/W German border, looking eastward into East Germany. It made the turn eastward along the southern border of East Germany, and then was supposed to make a big 180 turn to the west. The pilot's readout showed him what the navigational computer driving the plane was going to do a few seconds ahead of the aircraft automatically making the maneuver. Instead of seeing it prepare for a 180-degree turn, he saw it set up a 270-degree turn...which would have sent them directly into East Germany.
So, he turned off the computer and took manual control. The problem with that is in the SR-71, the navigational computer controls everything regarding navigation. Without it, they didn't even have so much as a compass. They were flying over an overcast sky, so they couldn't even see the ground. The pilot made what he reckoned to be a 180-degree turn so that they were at least heading west...as far as they could determine. But the imperative thing was to get to the English Channel, because that's where their refueling plane would be waiting. They couldn't land unless they refueled.
Every few minutes the pilot made a turn that he estimated kept him over western Europe, but they were essentially lost at MACH 3 and running out of fuel.
Where I was sitting in Omaha, NE, in the SACRECON Operations Center, we were in constant radio contact with the crew. Even though they were flying blind, lost, and running out of fuel at MACH 2, the pilot betrayed no excitement. He maintained that same laconic "astronaut-style" calm monotone: "SACRECON, we have a problem here."