"Smooth blue" uniforms for non-commissioned personnel were introduced in the 1950s, first for Warrant Officers. By 1956 NCOs of all ranks (corporal and up) were permitted to buy "smooth blue" uniforms at their own expense. Another innovation of the period was raincoats, hitherto worn only by officers. Despite the rainy British climate, the only weather protection for airmen outdoors was either their heavy winter overcoats or the rectangular 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.