Final Fantasy V/Airship

Searching for the crystal
There don't seem to be any specific clues on where to go next, but even if you just wander around in the airhip at random you will eventually fly over Gorn Town, and this triggers a cutscene. There is rumbling noise and a huge spaceship rises out the sand and flies away. Gorn Town is now gone and replaces by desert.

This should be reported to Cid and Mid, so go back to crescent island and land on the grey square that marks the entrance to the airship hangar. When you arrive Cid and Mid are already aware of what happened. They've found a book that says the Earth Crystal is inside the spaceship and is being used to power it. Reina is worried that perhaps her father was piloting the ship, but can't believe he would do something like that. The airship can't fly high enough to reach the spaceship as it is, but if you can find Adamantite then Cid and Mid can attach it to make the airship go higher. Galuf says he remembers seeing some Adamantite on the meteor where he arrived. (Note, it's easy to miss this clue if you're in the habit of quickly paging through dialogs, and if you do it can mean hours of pointless searching for what to do next.)

It a good idea to go further into the hangar to rest and save, then go back to the airship and check the ship's wheel to take off. Land at Tycoon Meteor where the game began. When you approach the meteor Galuf presses a hidden switch that opens the door. Go in and check the blue rock on the far wall to get the Anamantite. As you try to leave you realize that the stone was guarded and a battle begins.

Go back to the airship hangar to find Cid and Mid waiting for you. Cid and Mid go to work installing it while go have a rest. Later, just as you're waking up, Cid and Mid announce that the airship is ready. But they've also learned that the floating ruins are guarded by cannons.

Now when press the button to land the airship you can also go higher instead.

Floating ruins
When you're ready, ascend to find the floating ruins; it doesn't matter where you do this since it will be waiting for you. There are four set battles here you must complete. At the top of each wing there are two cannons, simply approach one from the front to start a battle with it. For each battle you have to defeat two cannon-like monsters, either FlameThrow x2 or Rocket Gun x2. While not actual boss battles, and not very difficult, you do need to take them seriously. Use Bolt based attacks when possible. Also, one of your characters may get confused during battle and since at this point they can be as dangerous as the enemy you're facing, make sure you have a character with a weak weapon so you slap someone in the face without doing too much damage. It's a good idea to have the Learning ability equipped on one of your characters since both types of enemies have Blue spells. Finally, don't forget to heal between battles; in fact you can land temporarily to rest without affecting your progress. When you've cleared all four cannon locations there's a short scene where the final gun appears. Fortunately you can land to rest and or save before taking this on. When you're ready, take off again and start the battle by checking the gun in the middle.