The point that QF seems to miss is that Air NZ has not opted to fly through ash and hope for the best. As they repeatedly imply. We are avoiding areas of ash by flying under/around them. With the full support of CAA. It is not a question of ash concentration. We are avoiding it completely. The accuracy of these forecasts/observations is validated by the fact that no aircraft has reported an encounter and no evidence of an ash encounter has been found on any aircraft. The crew briefs are very clear. No aircraft are to be operated into any area of forecast ash. If the ash level lowers to where it is impractical to operate then flights are cancelled. It is a question of risk management and this approach seems pretty sensible to me. If you look at a sat picture and see an area of CB's on your track, do you cancel the flight? No, you fly around them.