Put the summary of the bug you're having here

What I expected to happen was...:
I was expecting a fun elytra flight in a classic superflat overworld in creative mode while I was in offline mode.

What actually happened was...:
I dropped to the ground without gliding and became sad.

Steps to Reproduce:
0. Go in offline mode (no Wi-Fi)
1. /gamemode creative (if not set already)
2. Wear an elytra (mine was enchanted and renamed, if that could make a difference)
3. Fly up and try to glide
4. Fall and check whatever you check
5. Have an amazing day!