After you got the Airship, you followed a bird to Maranda, which is north of Cid's island.

Visit Maranda

In Maranda, go into the northeast house. Talk to Lola, read the letter, then agree to send her reply. Go out and check the bird next to the house. Watch where the bird flies, then go out and take the Airship northwest to the town where the bird went.

Zozo

In Zozo, check the bird and watch where it flies. Go north from the Cafe and look for someone walking around in that area. Buy Rust-Rid from him.

Go south, then into the Cafe, and go north until there are two doors. Go through the one on the right. Go up the stairs. The door on the right has a chest that contains a Tincture/Ether. Check the door on the left to use the Rust-Rid, then go in.

On Mt. Zozo, go northwest. Go past the stairs on the left and you will reach a chest. Then go back to the stairs that you just passed, and go south down them. Open the chest, then go south down the stairs. Keep going south, then go east toward the beam of light. From the light, go west, open the chest, then go north when you can, and continue going north. Open the chest that you find on the way, then go north through the door to find a chest outside. Go back inside, then go northeast and use the door to the outside.

Follow the path, then save at the save point.

Storm Dragon

If you are around level 70, step on the switch and walk up to the monster to fight Storm Dragon.

Otherwise, go south. You eventually reach Cyan's room. Read the letter, then go east to talk to him. There will be a cutscene. When he joins you, go east to the cliff that Cyan was standing on. You will find a key that unlocks the chest in Cyan's room. If you put Cyan in your party before opening the chest, there will be a cut scene when you open it.

With Cyan in your party, go back to Maranda, then go into Lola's house and check on the letter on the table. Cyan will switch it.