The rules for flight state “While charging, slam power attacking, or trample power attacking, this model does not stop its movement when it contacts an obstacle, an obstruction, or another model.”
But if a flying model is on the opposite side of a building and would have no line of sight to a model, it can’t declare that model as a charge target, correct? My understanding is that it would have to advance over the building and attack with no charge.
That’s correct, they still require LOS to charge. Flight lets them ignore other models for LOS when charging, but not other terrain. So if the terrain is tall enough to block line of sight between the two model volumes they wouldn’t be able to charge, but they could move over the terrain as an Advance if there’s enough space for them to land.
But if the terrain is short enough to see over they could totally make that charge.
