The Junkers J 1, nicknamed the Blechesel ("Tin Donkey" or "Sheet Metal Donkey"), was the world's first practical all-metal aircraft. Built early in World War I, when aircraft designers relied largely on fabric-covered wooden structures, braced with struts and exposed rigging lines, the Junkers J 1 was a revolutionary development in aircraft design, being built and flown only 12 years after the Wright Brothers had first flown the "Flyer I" biplane in December 1903.