When converting my server from 1.13.2 to 1.14, when I tried to use an Elytra they don't load chunks properly.  Just use an Elytra with some fireworks and try to load in some chunks, some chunks don't load at all until you hit the ground.  At first i thought this was just a problem with my world or something but I had a few friends try it out and they had the same results.  Not sure what causes this but it seems like a pretty big bug that should be looked into.