My question that I haven't really heard is this: the ash is mostly at quite high altitude, right? Couldn't the airlines therefore simply fly beneath it? I do realise that because of the increased density at lower FLs this would require greater fuel to generate greater thrust to overcome resistance, and would therefore be more expensive... but would it be prohibitive? Would the ATCs be set up to deal with this?
Hello, media man/woman. Times? Telegraph? ITN? In answer, yes we could, if allowed to. However:
There appears to be ash traces down to quite low levels (7000').
If you fly a large jet low level it burns much more fuel.
If you are flying low level you might drop out of controlled airspace, and start mixing it with light aircraft and gliders.