It looked like a cloud shaped like 1/2 an oval, high up but much larger than anything that is man made.

I was laying on my outdoor futon and this shape flew north to south directly above me but at a high elevation. It looked like the 1/2 of an oval and was larger than any man made craft…totally silent. I blinked twice because it did not make sense what I was seeing. It reminded me of a smoke ring moving fast, but only if you were seeing the front edge of the ring. It was clearly visible until my house obscured it. Never in my 51 years have I seen anything like this.