Of course this still leaves open the question of whether global effects that are not "attacks" or "weapons", like the storms of Njal and Imhotekh, can hit flyers. Mike Brandt says, yes they can.
Q: How do maelstroms, novas and beams – or indeed any weapon
that doesn’t need to roll To Hit or hits automatically – interact with
Zooming Flyers and Swooping Flying Monstrous Creatures? (p13)
A: Only Snap Shots can hit Zooming Flyers and Swooping
Flying Monstrous Creatures. Therefore, any attacks that use
blast markers, templates, create a line of/area of effect or
otherwise don’t roll to hit cannot target them. This includes
weapons such as the Necron Doom Scythe’s death ray or the
Deathstrike missile of the Imperial Guard, and psychic
powers that follow the rule for maelstroms, beams, and
novas.
Mike Brandt got over-ruled by GW.