One of the main ways that the United States guards against nuclear threats is through its participation with Canada in the North American Aerospace Defense Command (NORAD). Key elements of its mission are aerospace warning and aerospace control.
The NORAD website explains that aerospace warning includes the monitoring and detection of “man-made objects in space" and the validation of objects so detected, along with “warning of attack against North America.” These objects may be “aircraft, missiles, or space vehicles.” The NORAD-US Northern Command (USNORTHCOM) Command Center is maintained at Peterson Air Force Base in Colorado. There are three subordinate regional headquarters in Alaska and Florida (both in the United States) and Manitoba, Canada. Through these centers, data from worldwide sensors is collected and coordinated.
The technologies and related vehicles and hardware that NORAD employs include “satellites, ground-based radar, airborne radar and fighters”; they are used for detection and interception and, if necessary, will “engage any air-breathing threat to North America.”
In addition, US national nuclear deterrence strategy includes maintaining a nuclear arsenal within the country’s borders. The Department of Defense notes that these weapons are kept in missile silos and on submarines and aircraft. The Minuteman III weapons are ground-based, while the Trident II missiles are kept on submarines. There are several types of nuclear weapons intended for delivery by aircraft, including the B-2 Spirit and the B-52 Stratofortress.