Phantom Glider

Reason for Addition:  

Phantoms have little use in Minecraft; the membranes that they drop are only truly useful during late game, when you have an Elytra in need of repair. Their only other use is brewing Slow Falling potions, which have little utility overall. This would give a use to Phantom Membranes in the early game, when you haven't yet begun experimenting with potions or defeated the Ender Dragon.  

What it Does:  Works in a very similar way to the Elytra. However, they are slower, less durable, and fireworks cannot be used with them to boost. Offhand items cannot be held when using a glider. To activate the glider, you need to hold it and either do a running jump or jump off a ledge.  These restrictions are not too punishing, yet allow the item to exist in the game while not completely invalidating the Elytra.  

Other:  

Banners could be used on the Glider to customise what the top membrane looks like, similarly to Shields.  

Crafting: