For the uninitiated, “Nomex is a flame-resistant meta-aramid material developed in the early 1960s by DuPont and first marketed in 1967, an inherently heat and flame-resistant fiber that won't melt, drip or support combustion providing a superior barrier between what's inside (often a human being) and the hazards around it.” What none of the references will say is that when worn as any sort of attire (flight suit, jacket, long underwear) it’s highly efficient insulation, to the point that wearing a Nomex jacket in cool weather will feel way TOO warm, let alone on a 70-80 degree day or in the sun or in a hot cockpit.