Flying will become available in Zereth Mortis at the start of Week 4, but you can start working on the requirements now.Check out our Zereth Mortis Flying Guide for more details on how to complete these requirements.
EDIT (11:15am): In the final weeks of the PTR, the Campaign chapter required for A Means to an End was swapped, making flying available during week 4 of Patch 9.2 (week of March 15th (NA) / 16th (EU). We apologize for the mistake and have updated the article. How to Fly in Zereth MortisThere are 6 achievements that you need to complete in order to unlock Flying in Zereth Mortis. All of these achievements are available at Patch 9.2 launch except for A Means to an End, which becomes available at the start of Week 4.
Explore Zereth Mortis Curious Collections Path to Enlightenment Tales of the Exile Adventures in Zereth Mortis A Means to an EndFor Exploration, Treasures and Rares, you have 2 weeks to slowly finish off these collection items before Chapter 5 unlocks and A Means to an End is completable. If you want a full list of these collectables, check out our Zereth Mortis Flying Guide The two other achievements require a little more direction, shown below.
Path to Enlightenment LocationsFor Path to Enlightenment, these quests start at the following location:
Look Who I Found! in Haven /way 34.6 66.2 Enlightened Exodus in Haven /way 33.8 64.6 Lost Grace in Pilgrim's Grace /way 61.8 53.6 Tales of the Exile LocationsFor Tales of the Exile, players must find these pages around Zereth Mortis. When you're close to these pages, it will appear as a large yellow dot on your minimap. However, they aren't always available and seem to respawn about every 5-10 minutes.
Firim in Exile, Part 1 — on the ground Read more on wowhead.com