For which resources does PL4 apply according to USAF guidelines?

PL4, or Protection Level 4, according to United States Air Force guidelines, pertains to resources that are essential for the operational capability of the Air Force and could cause significant harm if compromised. This level is designed to safeguard assets that, if lost or compromised, would have a substantial and detrimental effect on the ability to perform critical missions.

Resources classified under PL4 typically include key weapons systems, critical infrastructure, or vital information that directly supports operational capabilities. Protecting these assets is crucial for ensuring mission success and maintaining a strategic advantage. Therefore, the focus on operational capability aligns directly with the criteria used to establish the PL4 classification.

In contrast, publicly accessible resources do not typically fall under such stringent protective measures, as their compromise would not adversely affect the Air Force's operational effectiveness. Resources that do not directly impact war-fighting capabilities also do not meet the criteria for PL4 classification, since the focus is specifically on those that would hinder operational efficiency or effectiveness.