the titling. Since type is designed to be customarily read from a flat surface, airline livery type is often modified to fit curved aircraft surfaces. The specifications result in a logotype: a cliche of type whose characteristics remain unchanged. The airline's monogram or emblem is defined in terms of geometry by graphic designers. The resulting specification is called a logo. Logos are also modified to fit curved surfaces and appear identical from diverse viewing angles. The colour or colours are specified in terms of colour matching and standardisation systems like Pantone or Federal Standard 595. The resulting specification is called a colourway. Individual aircraft types most often have individually designed liveries which appear to be identical, but are not quite the same as those applied to other aircraft types operated by the same airline. Uniform liveries became generally adopted by the 1950s and '60s. Before then, individual airlines, notably Aeroflot and some US carriers like Delta Air Lines, used custom liveries designed for each individual aircraft type they operated. Aeroflot abandoned the practice as late as 1974, adopting a uniform livery across its fleet. Standard liveries Bare metal Until after the Second World War, the "default solution" for aircraft livery design was to leave the aircraft exterior unpainted and decorated only with the airline's title, plus possibly an emblem or monogram. When the world's first all-metal airliners, such as the Boeing 247, Douglas DC-2, and Douglas DC-3, entered service in the 1930s, the sleekness of their shiny exteriors provided an imaginative canvas for livery design. At the time, paint was expensive, fairly heavy, had relatively poor adherence to metal, and was prone to early bleaching, mechanical, and chemical damage; leaving the aircraft skin largely unpainted was logical and economical. As corrosion and paint research advanced and airliner lives lengthened, airframers began applying advanced primers and treatments to airliners during manufacture. Many airframers insisted on overall corrosion protection remaining in place throughout an airliner's service life, or at least throughout its diverse guarantee periods. This made bare metal liveries problematic; they began giving way to painted exteriors by the mid-1960s. To ensure longevity, bare metal liveries involved intensive polishing and waxing during manufacture and in service. Nevertheless, the bare metal era survived into the 21st century and the advent of plastic composite airliners like the Boeing 787 Dreamliner and Airbus A350 XWB. The most notable proponent of the bare metal look,