It's bollox - at least at FL055 where I flew ~ 400nm today, or below. Vis is mostly unlimited, and there is no way for "dust" to be around with that kind of vis.
Higher up, possibly. I was just above the tops (below cloud it was rough as hell, as usual on a warm day) and there were some quite dark layers at maybe FL100 plus.
Apparently Farnborough were ordered to offer a BS only. Probably to stop exec jets operating VFR, contravening their company manual to always have a radar service when OCAS
