ground sheets issued for all soldiers' use on campaign. Regulations were altered in the 1950s to allow airmen to wear raincoats bought at their own expense. During 1975/6 the wartime "Hairy Mary" working dress uniforms were replaced for all ranks with the 1971 pattern No 2 uniforms. Made of a smooth woollen and man-made fibre mix material the jacket was a loose blouson design with a front zip fastener and epaulettes, often referred to as a 'Thunderbird jacket'. In the mid 1980s RAF blue crew-necked woollen pullovers were replaced with a new V-neck design featuring blue-grey cloth elbow and shoulder patches plus a pen holder patch on the left sleeve. The Thunderbird Jacket was withdrawn in the 1990s and replaced with an additional pullover, the design reverting to a round neck but retaining the pen holder, the official description being Jersey Man's (Woman's) Blue Grey Round Neck. In the 1990s an RAF blue nylon foul weather jacket and overtrousers were issued. Although not initially intended it quickly became standard practice for officers and other ranks to attach rank badges to the lapels and wear the nylon jacket in place of the uniform raincoat, as a more practical modern wear. Disruptive Pattern Material Disruptive Pattern Material (DPM) was the combat uniform in RAF use until 2010, when Multi-Terrain Pattern (MTP) uniforms began replacing it. Ranks and insignia The Royal Air Force ranks and insignia form part of the uniform of the Royal Air Force. Royal Air Force rank insignia were based on combination of those of the Royal Navy officer rank insignia and British Army. Notes Aircrew Flying Badges Aircrew Flying Badges are qualification badges worn on the left breast, above any medals, by personnel in the RAF who have passed certain qualifications and criteria. The Royal Air Force currently issues three different flying badges, though older discontinued badges may continue to be worn. These three flying badges are: Pilots badge: the letters "RAF" in a brown laurel wreath, surmounted by St Edwards crown, with a swift's wing either side. Weapon System Operators: the letters "RAF" in a brown laurel wreath, surmounted by a crown, with a single swift's wing on one side. Airborne Specialists: a half wing, without crown and 2 letters in the centre. The letters correspond to a role, e.g 'AT' - Airborne Technician. As of 2021, Qualified Space Personnel wear 'UK Space Wings': a silver delta, an