Minecraft wiki entry for Best_enchantments_guide, associated text: It is almost necessary to apply these two enchantments to elytra, as they are one of the most useful modes of transportation in late-game. Unbreaking is needed to quadruple the elytra's airborne time, since elytra breaking in mid-air can be deadly; Mending is the most effective way to repair elytra, as otherwise they can only be repaired with phantom membranes or other elytras in an anvil, and the cost increases over time.