Lord Adonis on R4 now [live transcript - all errors mine]- "there is a differentiation between the dangerous area, a no-fly zone, and a low contamination zone where on the advice of manufacturers and test flights where it is safe to fly. The safety regime has been changed to significant analysis of test flight data and experience of flight, and crucially advice from aircraft engine and airframe manufacturers... before last week, volcanoes weren't a problem in Europe. it's because we faced this act of God that we had to face this problem, and intensive work by manufacturers to establish how it is safe to operate."
Interviewer: Were you aware that there were all these planes in the air heading for London?
LA: Of course I knew this evening, because it was all over the media
Interviewer: Didn't BA tell you?
LA: All I needed to do was turn on the television. The process to clear airspace has been in progress since the beginning of the week.