I got this nice, interesting piece recently. It is for RAF flight personnel (not ground crews). It is made out of Nomex (Aramid) and follows the standard jacket cut pretty closely in most respects. The two big differences are a velcro collar tab and a padded arm pocket on the left arm. Note the damage to the top edge of the pocket seam. The guy who sent me this said he's seen a few others and all had the same damage, so it appears to be a significant manufacturing defect.
Interestingly the tag makes no mention of this being a special garment. My contact was told this was in case of capture the crew could, in theory, avoid being detected as such. I don't know if that's true or not, but it is one logical explanation for the tag's nomenclature.
Unfortunately the trousers are near impossible to get a hold of. Bah.