Qantas just saving fuel? Not likely. Rumours persist -- we've had at least two -- that Qantas' decision to ground flights rather than fly around the gritty volcanic plume is more to do with costs and not safety. As one tipster, the imaginatively named "Top Gun", explains: "It is no secret amongst pilots that the lower an aircraft flies (below a plume of volcanic ash for example) the higher the consumption of aircraft fuel. This translates into a less profitable flight for Qantas."

Our resident aviation guru Ben Sandilands reckons the figures don't add up. He wrote on his blog Plane Talking yesterday: "The aircraft that are not flying aren’t earning their keep. The numbers will vary depending on whether the jet is attracting finance or lease charges, or is owned. But even then there are continuing support costs not just for labor, but for systems support, and those fixed costs end up being divided by fewer aircraft as a result of part of the fleet not flying say Tasmania routes." Can we put that one to bed?