Shadowlands flying works pretty much the same as the Draenor or Battle for Azeroth flying. You have to overcome a serious of challenges and do a bunch of quests in order to be able to fly over Shadowlands zones. All of them but the Maw and Korthia. This time it is a bit easier though. You need to finish your covenant campaign, unlock Korthia and complete Korthia campaign. We can do any of that for you as a part of our Shadowlands flying unlocking service.
ETA for the boost is 1-2 days, depending on your current progress.
Shadowlands flying unlocking rewards: