Artillery uses its own to hit modifiers separate from regular attacks. There's no penalties based on target status for artillery attacks. In either artillery rules set (standard or advanced). Now if you're doing a direct fire shot instead... yeah I think all standard modifiers apply in addition to the direct fire penalty. Again, on something minxy like a VTOL, it'd probably be another low probability attack... DF shots really only work out well when you can shoot the ground under the target and that doesn't work so well if the VTOL is of sufficient altitude.
It was more a question of what's possible.
According to the erratum you linked, it would while it's airborne.
So to further clarify. A VTOL that wishes to fire ADA -MUST- be on the ground when it fires it?
Other artillery attacks (other artillery types or direct-fire Arrow IV) can only be made while grounded.
The scenario I am envisioning right now is a lance of Yellow Jacket
Arrow IVs. These flying at say, 80" above the ground would be effectively immune to ground fire.
Each of them would then be able to make an ADA attack against any aerospace in the central or inner ring for a target of 3, 5, or 7. That's up to 8 damage per turn with very little ability to counter it.
If an Aerospace were to make it past the inner ring to engage them, they would need a 9 to hit one with a strike attack, but would be subject to ground fire.
Does that sound correct to you?