When I was flying around with an Elytra on in the Nether and died, when I respawned back into a bed and jumped it caused the Elytra to enter its "flight" mode. There is no propulsion, but when smacked by another player it launches you similar to a firework. Removing the Elytra does not remove the "flight" effect. The effect fixes when crouched.

https://imgur.com/a/f6i8GM1