Lord Adonis stated on 'The world at One' today that there had been an over reaction to the Ash event by the authorities concerned.
Reaction was based on long-standing international safety proceedures, and especially on manufacturers' (both engine and body) zero-tolerance of volcanic ash. They have (apparantly) revised this tolerance upward by 10x, but as any child knows 10x0=0!
It begs the question: why did Adonis not make this change before? But we know from this morning's Guardian that airlines have opposed revision for their own legal/economic advantage.