When using Elytra, it will go down to 1 durability and stop working. It never breaks. Not sure if this is intended or not.
Reproduce:
1. Use the command /give @p minecraft:elytra 1 425
2. Go in survival
3. Go up to the sky or use /tp @p ~ ~50 ~
4. Glide around and you'll notice that it goes to 1 durability, never breaks.
I believe this is intended, apparently it has a different texture. This suggests that they are too precious to have break, and just stop working.