Ultima Thule, a broken and stagnant zone, is your final destination in Final Fantasy XIV: Endwalker. Following the tradition of expansion final zones, this zone is story-heavy and will require the completion of the Main Story Quest to access the later islands of the zone. Collecting your last few Aether Currents is easy — all of the overworld Aether Currents are simple to access. As with other zones, there are 15 Aether Currents, split into 10 overworld currents and 5 quest currents.
The 5 quest Aether Currents can be located on your map as you progress through the main story, indicated by a Quest Icon with a plus symbol on it — except for the final one, which is given as a reward for finishing the Main Story Quest in the zone. However, to find the overworld Aether Currents, you have to search yourself. By accessing your Aether Compass — no longer a key item, but instead placed in the Collections tab, under the Duty section of your menu — you can find the general location of the closest Aether Current to your character.
Remember that the second and third islands are locked behind Main Story Quest completion but otherwise are easy to access. Most of Ultima Thule is flat and barren, with only the occasional environmental object — none of the currents are hidden behind anything or tucked away in a corner. However, there are plenty of enemies, so keep your guard up as you hunt down your last flying unlock.