Why did women have to work during World War 2?

During World War 2, many men joined the military. They left their jobs. Someone had to run the machines and make the products. Someone had to work in the stores. Someone had to run the businesses. Henry Ford hired women to work in his factories. He taught women to fly the airplanes that he built for the war effort and to fly them to the troops on the front lines. They flew with loaded guns so that if the enemy appeared, they would shoot him down. I do not know if any of Henry Ford's female pilots delivering planes ever shot down an enemy aircraft.