It's tricky. This is taken directly from GameFaqs- we get this alot.

How do I land on Palamecia? ^[2J]
I (Action) have been getting a lot of emails on this one. Seems people can't get the airship to land on Palamecia.

Here's what I wrote in my FAQ:
To get to into Palamecia, you'll need to descend upon it using the Airship. The
spire on the top of Palamecia will be your guide. Center your Airship right
above the spire, then go up one space and try to land.

If you can't seem to land, try this. Move up one space, try to land. Move left one space, try to land. Repeat this in all directions on Palamecia and you'll eventually land. Use this guide if you don't understand:

. _ _ _ .
. _ 1 _ .
. _ _ _ .

1 is where you start. Try all 9 spaces and you'll be able to land on one of them. Make sure the airship doesn't move two spaces, since it likes to move really fast.