So there is a direct pathwy between Coerthas W. Highlands and Ishgard...

[Morningstar1337]

But none of the Aetherytes in Ishgard can take you there. Why is this the case? it's a little strange

[Enkidoh]

Probably because that is no actual path on the ground (it's blocked off physically by the icewall at Snowcloak) but it's kind of handwaved away that you actually fly your chocobo between the two (this is why the actual zone line cannot be accessed until you have at least one flying mount). The other zone lines in Ishgard (like to the Sea of Clouds and even the entrance to the Aery) are explained in the same way.

Basically they're docks where you're not heading on foot but actually flying between the two points.

[Rhode]

Even if they made it teleport you there, you would be literally a second away from Falcon's Nest.

[Stupiduglytaru]

Ya but teleport :3