I finished the DLC a while ago and i wanted to go back into the airship. Unfortunnatley when I arrived I discovered the enemy drones are still all around the airship and the gate to the garden had shut. I cannot open it and was wondering after reading this if there was a way to open it. All entrances on the bottom of the ship closed and because there is no black hand the terminal thing you need to destroy to open the top hatch cannot be reached.
There's no way to reopen it, but there's 2 things you can try:
Notice that there are windows in some areas of the airship. You can kind of see into some places.
See Just Cause 3 Bugs and glitches. There's a way to get a plane from a crashed train and use it to fly through solid matter (like the ground and buildings). That could possibly let you get back in there. The same technique can be used to enter the Hive. The Hive article has additional videos, if the glitches article is hard to understand.