[Jonah Hex]

The X-1A had an uncommanded roll due to roll-coupling with Yeager aboard and lost 30k' before he brought it under control.

Of course, Mike Adams bought it in an X-15 when it went out of alignment prior to reentry. Some blamed it on pilot vertigo, while others blamed it on the stability augmentation system.

[Lx]

They had an X plane show on Discovery wings and the only accidents I remember them mentioning for the X-15 was the exploding engine on the test stand and the one that cracked on landing.
Anyone else see the show, did I miss something?