When I was flying around with an open hand, the elytra only displayed a transparent outline. But I'm writing this because I noticed certain non solid blocks (such as item frames and water) facing the east - west are always invisible behind it, but north - south blocks are invisible only under level 80.

I was expecting the elytra to render normally holding any item the same as nothing. Instead, it became partly transparent and certain non-solid blocks became invisible behind it.