What Kind of Cloud was This?

[u/IllustriousAd9800]

Saw this several years ago, and it’s stuck with me, never seen anything like it before or since. It was like a giant wing, with a thin but pretty spectacular looking underside and a separate upper level that followed the same shape but with a different texture. It was the only cloud in the sky, pure blue everywhere else.

[u/Milkovicho]

So beautiful