Flying suit is not an official uniform - it is a "coverall" and therefore only to be worn at work
Wensleydale. IIRC the Flying Suit (not coverall) is in fact designated No 14 Uniform - a change that occured in the mid/late 90s and again, IIRC, was something to do with captured behind enemy lines and being out of uniform. Under these circumstances you may not be afforded the protection of the Geneva Convention or something along those lines.