Bug with an Elytra.

If you wear elytra, start running and doublejump,then hold space and when character will hit ground and jump, very quick tap space again. Repeat that process to speed up ur character using an elytra without fireworks.

Video

I guess that player`s velocity and direction does not clamps to player`s normal speed instantly(elytra speed is ~33bps and player`s speed is ~5 bps and when player on elytra with 33bps speed lands, his velocity doesnt decrease to 5bps instantly)...

So, when player is jumping he gives himself ~1 block height, glides from it on elytra, and when hits ground, instantly jumps again, so on next jump velocity stays same from prev. jump and increases during the glide.