Plummet Mod 1.12.2 gives you the ability to limit the in-game players from flying in some circumstances in Minecraft.

This is a Server Utility mod, so you will have to install it on the server side. When you use it, you can restrict the players in the game from flying in some circumstances. Players cannot fly by default.
Then, you can use GameStages to configure the mod. This will let flights be enabled again for some players.
Plummet Mod helps you manage the flying ability of players.
Requirement:
- Minecraft Forge
Instructions
- Minecraft Forge must be installed in advance.
Minecraft Mod 1.12.2