Current bases in Romania, the Philippines or Kyrgyzstan might fall into this category.

CENTERFORSECURITYPOLICY: Rebasing -- and Reequipping -- for Transformation

Twenty-five nations, nearly a quarter of those assessed, hold a Category 2 ranking, including the Philippines, Bangladesh, Barbados, Cote D'Ivoire, Ghana, Indonesia and Israel.

CNN: How do you know your airline is safe?