Under the gunship, in the little camp to the right, there's a portal to get back up onto the ship.

If you do not take this portal, and end up porting back to Org, then you need to go to the monk trainer/pandaren area and use the portal to get back to Pandaria.. Then make your way to the camp and find the portal to the airship.

It's red and has a little blimp looking icon over it.