Void Mine and scenery

Yesterday I played a game with one of my friends, and he had placed his havoc squad inside a ruin with a roof. I flew over the building with my Voidraven bomber and dropped the Void Mine on his havoc squad, killing 8 members.  

But now I wonder if I truly had the right to do so such a manoeuvre ...
The fact that the wording of the Void Mine rule doesn't mention anything about cover or buildings doesn't help.

From a lore/realistic perspective, I would say I had the right to drop the Void Mine, because of how powerful it is and how fragile a ruin is (I mean a cracked roof won't protect the victims from a weapon capable of literally disintegrating anything unlucky enough to find itself within its blast radius)

However, when it comes to tabletop rules, I must say that I am uncertain.

What do you guys think ?

Unless it's an enclosed building with a "transport" capacity that would remove the unit from the board, they are fair game as targets. Being in cover doesn't enact the "embarked" rule so they're still on the board so you can fly over them and drop the bomb.

There's also nothing in the rule requiring line of sight. You only have to move over them in the movement phase. I'd say that's entirely legit, and probably one of the best uses for the voidmine. Ideal for shooting units buried in cover who don't need LoS, like hive guard and IG mortars. Provided it's a big enough unit to generate a decent number of dice anyway!