In a singleplayer world it is possible to be kicked for flying.

What I expected to happen was...:
I built a TNT launcher thing to use the elytra by being launched up really high. (over 600 blocks).

What actually happened was...:
Instead, I was booted.

Steps to Reproduce:
(note - some steps may not be necessary but I decided that my computer is too slow for exhaustive testing)
Build a TNT 'launcher' with 24 (48 to be 100% sure) dispensers dropping tnt into a 3x3 ring of water, where the center of the ring has a fence. (might need to be an amplified world?)
Go into survival and stand on the fence in the middle of the ring, and activate the dispensers with redstone. When the TNT explodes, you should be launched up (if you don't die from the blast, so use peaceful mode) and then around 400 to 600 blocks up be booted for flying, or have your game crash (and upon looking at the log, find that you've been booted for flying).