Columbia subject headings:
Air defenses--United States--Planning.
Military planning--United States--21st century.
United States. Air Force--Appropriations and expenditures.
Harvard subject headings:
Air defenses--United States--History--21st century.
Air defenses--United States--Planning.
Military planning--United States--21st century.
United States--Military policy.
United States. Air Force--Appropriations and expenditures.
United States. Air Force--Technological innovations.
Princeton subject headings: