if anyone here has played Warhawk on PS3 they'd know matt's right. the clouds are ridiculously well-done volumetric clouds which the players can fly-through and hide in (at least somewhat; the markers above players in team-death-match make it still hard not to attract attention).
placing an aerial-mine in a cloud, for example, is a great way to conceal it.
also, when using the tow-missile, a cloud is a fairly well-hidden hiding spot.
nice clouds:
julz