icon or text for Quests that require flying?

[Felis]

No mainstory quest before meeting Tiamat in Azys Lla require flying
You don't need the side quests to get to Azys Lla

that is not true. i have yet to attune/unlock flying in any of the 6 zones and i have been able to take on quests that require flying.
they are unlocked by story progression and other quests.

The devs made it that at a certain point in the side quest chains most players will unlock flying.
If you can't fly, than it is because you missed some aether currents in the open world or there are still some sidequests with aether current as reward.
If you don't want to fly, and the sidequests start to require you to fly, then it is time to move to the next zone. Because you reached the point where the devs think the players should have unlocked the fly for that zone.