(CNN) - Hillary Clinton called on the United States to take out Syrian leader Bashar al-Assad's Air Force on Thursday, days after a chemical attack killed more than 70 people in the war-torn country. "Assad has an air force, and that air force is the cause of most of these civilian deaths as we have seen over the years and as we saw again in the last few days," Clinton said in a speech at the "Women in the World" summit in New York City. "And I really believe that we should have and still s