How Do US Combat Air Patrols Maintain Airspace Security?

The United States routinely operates combat patrols to maintain security. These patrols include establishing a defensive zone to prevent enemy aircraft from penetrating friendly airspace. While some aircraft, like the P-8 Poseidon, are used for maritime patrol, others, like the F-22 and F-35, are used for combat patrol and interception. For example, NORAD recently tracked two Russian and two Chinese bomber aircraft on a joint patrol in the North American US Air Defense Identification Zone.