After doing quests on my alt, I found out that the "Airborne again" quest from Azshara should be marked as a breadcrumb and becomes unavailable if you complete the quest "Where's My Head" with some trial and error on another character.

Relevant quests:
https://www.wowhead.com/quest=24497/airborne-again
https://www.wowhead.com/quest=14462/wheres-my-head

@Darkal31