1 Discard any hammer with mushroomed or chipped face or with cracks in the claw or eye sections. 2  Wear safety glasses or goggles, or a face shield (with safety glasses or goggles).  Strike a hammer blow squarely with the striking face parallel to the surface being struck.
The first jet airplane was the Heinkel He 178 made in Germany in 1939, right before the outbreak of World War II .
History >> World War I. World War I was the first major war where airplanes were used as a significant part of the military. The airplane was invented by the Wright Brothers in 1903, just 11 years before the start of World War I.