With this datapack (it works in singleplayer and multiplayer) you can fly in a helicopter.
It even has some nice features such as a turning rotor and sounds.

Drop the datapack in the datapacks folder of your minecraft world. Then open your world and type /reload. You'll get two spawn eggs, one to spawn the helicopter and one to remove it.

The control is very simple. Sit in the helicopter and start the engine. Use the 3 glass panes to control the helicopter and look in the direction you want to fly.
Use the debug to get information about the altitude of the helicopter.

The helicopter has 100Healthpoints. It can be damaged by shooting an arrow on it or flying into a wall.

Have fun! :)