How to get back to Dorga's house?

After beating Titan and getting new jobs including Warlock and Shaman. None of the NES GameFAQS walkthroughs give me the valid info to return to Dorga's House, and the walkthroughs on YouTube seem to skip this part altogether...?

I am supposed to fight Dorga and Unne now, but how do I get back? I keep getting blasted away by an invisible wall whenever I use the Invincible airship or any character by the entrance towards the house.

Switch back to the superfast airship, the Nautilus.

Ok now I am confused, wasn't the Nautilus destroyed by cannons? And how exactly can I switch between ships anyway???

The Nautilus is the one that goes underwater as well. It will be parked outside the cave you went in to find the Falcon. (I think that is the super airship's name)

Ah, found the ship a few days ago. Thanks.

Then I beat the game, the final levels were nice!

By the way, I am busy with a Final Fantasy marathon from 1 to 12 excluding 11. Never got around to beat any of them, until now.