After obtaining your airship, its time to make your characters stronger and upgrade their job classes. To do this, head north to the islands dotted with yellow location marks. The caves are loaded with treasure and no enemies, so take the time to search them out. In the caves you will meet dragons. They are the friendly tribe ruled by the king of dragons himself, Bahamut. After meeting with Bahamut he will instruct you to bring him a symbol of your valor. To do this take your airship to the west until you see a castle like structure. You will have to abandoned your airship a good ways away from the castle and make the treck on foot. When you reach the castle, now known to you as the cave of trials, an old man will instruct you to sit on the throne. After doing so you will be teleported into the trials yourself. At the end of the cave is your reward, the rat's tail. Return to Bahamut with your treasure and he will acknowledge you as heros. Each class has a special feature as follows:

Warrior to Knight: Has a larger attack increase during level ups and can use minor white magic from levels 1 to 3.

Thief to Ninja: A great increase here. He obtains more power and endurance and becomes a warrior like class. He can use all weapons the warrior could, and can use minor and moderate black spells ranging from levels 1 to 5.

White Mage to White Wizard: Not much of a change really. Gains more attack and a better increase in intelligiance and spell use. Aslo gains the ability and right to wield the strongest white spells in the game.

Black Mage to Black Wizard: Gains an increase in attack power and a great boost in magic use. But where he really shines is his use of the strongest and coolest black magic spells in the game.

Red Mage to Red Wizard: Not much of a change, he gets spell use increase... but only equal to that of what the White Mage and Black Mage used to get before class change. He gains an additional attack boost, as well as stronger black and white magic spells.

Monk to Master: In my opinion, a must have in your party! With no equipment what so ever on, my Monk gained great defense bonuses as well as an outstanding attack increase. He was doing well over 1,000 damge while my knight was only doing 400. An over all must have in your party if you are a first time player.