I recall hearing how the US Air Force was investigating reports of UFO's, and was surprised to find a 'real' one closer to home.
Highly unstable more than a few feet off the ground, it never proved viable. Unfortunately nobody at the time realized they might have been onto something if they'd pivoted to inventing the hovercraft.
The sole surviving XB70, another super cool plane that was obsolete by the time it was ready, is a valued museum piece. These planes should have been.