versions of their rank insignia stitched in the centre of the upper sleeve, although for a period in the 1980s these were stitched onto slip-ons, ostensibly to save wear-and-tear on the uniforms, but also providing the ability to remove rank for security purposes. The national identifier consisted of a "CANADA" flash stitched on the upper shoulder just below the sleeve seam, and unit or trade identifiers were worn on slip-ons on the shirt's epaulettes; however, personnel belonging to Canadian Forces Europe and other overseas missions wore full-colour Canadian flag patches on the upper sleeve. In the 1990s, the "CANADA" flash was replaced with a subdued olive-drab Canadian flag, worn on the upper left sleeve below the epaulette. These flag badges showed up in full-colour red and white when illuminated by a blue light. Flying suit Canadian Armed Forces aircrew wear green flying suits as operational dress. The two-piece flying suit (originally worn only by tactical helicopter crews) and the one-piece coverall flying suit are worn interchangeably by most CF aircrew. Prior to the mid-2000s, the one-piece flying suit was blue and worn by all fixed-wing aircrew. Naval combat dress RCN personnel wear naval combat dress (NCD) as operational dress. NCD consists of a blue shirt, black pants, and black jacket or parka for colder weather. Originally designed for wear on board ship, naval combat dress is made of Nomex. Occupational Dress Various types of special working uniforms are worn by military police, medical personnel, dental personnel, cooks, chaplains, firefighters, stewards, and brass-reed musicians. Unlike operational dress, occupational dress uniforms are worn only by personnel actively engaged in designated tasks. Within the CAF Dress Instructions, maternity dress is also grouped in this category of "occupational, health, and safety dress". Maternity dress When conventional pattern uniforms are no longer comfortable or aesthetically appropriate, a pregnant woman can wear maternity dress. The non-operational maternity dress is a common-pattern ensemble in light-weight, washable material in three environmental colours. There is also a white occupational variant for medical, dental, and food services personnel, worn as well by navy personnel during the summer dress period. The ensemble consists of general-purpose items suitable for wear as alternatives to those of service dress and its ceremonial and mess derivatives. Medals and accoutrements may be worn on ceremonial dress occasions. The ensemble includes a long tunic, a short tunic, slacks, maternity shirts in both long and short sleeve, a