Abso-fething-lutely. Orks should love flyers, because their shooting is woeful to begin with, and there really is no difference between a Thunderhawk and a Chimera to them. Without AA mounts, absolutely everything needs 6s to hit, and blast weapons cant hit them at all. Want to kill a flyer? Bring AA. Failing this? Spam missiles. One of them will hit sooner or later!