Definition
The executive department of the United States federal government responsible for coordinating and overseeing all agencies and functions of the government concerned directly with national security and the United States Armed Forces (Army, Navy, Air Force, Marine Corps, and Space Force). In the aviation context, the Department of Defense operates and controls military airfields, joint-use airports, and special use airspace, and it works with the FAA on matters affecting both military and civil aviation, including airport status, charting, and procedures.
Plain English
The part of the U.S. government that runs the military. It owns and operates military airfields and works with the FAA on anything where military and civilian flying overlap.
Context Anchor
Seen in FAA airport and procedure information when a facility, restriction, or procedure is connected with U.S. military operations.
Derivation
Department means a distinct part of an organization assigned to a specific kind of work. Defense means protection. Together, Department of Defense names the U.S. government organization responsible for national military protection, which helps explain why the term appears around military aviation facilities and procedures.
Why Pilots Care
Some airports civilian pilots use are owned, operated, or partially controlled by the Department of Defense. Knowing this matters for prior permission requirements, restricted access, special procedures, and understanding why an airport's status (open, joint-use, or closed) may change.
Intuition Check
Do not read this as a general phrase meaning any group that provides defense or security. Capitalized as Department of Defense, it means the official U.S. federal department that runs the military.
Example Sentence 1
Because the field is operated by the Department of Defense, civilian pilots must obtain prior permission before landing.
Example Sentence 2
Pilots planning routes near military fields should verify any Department of Defense restrictions in the current NOTAMs.