Put on your wings and make rockets
Check the chest slot: elytra in the hotbar does not work. When falling, press jump again, then direct your gaze to change the trajectory. Looking down accelerates, looking up slows down and consumes the accumulated speed. Reference: Minecraft: elytra.
Recipe for simple rockets: 1 paper + 1 gunpowder gives 3 rockets with a flight duration of 1. Two or three powders increase the duration of acceleration, but for the first control short pulses are more convenient. Don't add a fireworks star: the explosive rocket can hurt you in flight.
One training circle
Start on a low ledge above a wide strip without trees. Open your wings, straighten your trajectory and use one rocket. Do not press it into a wall or under a low ceiling.
Choose a place to land in advance. Smoothly reduce your speed by raising your gaze and descend along the ground; turning sharply near a wall is not a substitute for braking. Our target training lane is 30×10 blocks, but this is a convenience for training, not a guarantee of any speed.
The repair procedure with new experience is described separately: Mending in Minecraft: repair equipment with experience.
Check durability before flying to the edge of the map
When the working safety margin is exhausted, the wings stop flying. Keep your supply of rockets separate and don't cross the void with nearly broken elytras. The Unbreaking and Mending enchantments reduce maintenance, but do not cancel the pre-takeoff check.
On the first long routes, mark alternate landings and home coordinates. Low over unknown terrain, loading chunk delays and sudden obstacles are dangerous; the altitude reserve is more useful than constant acceleration near the ground.
Recording coordinates and road signs are described in the manual: Maps and signposts: make your world easier to navigate.
