What must US airports have unless specifically requested by a US military service?

US airports are required to have a published Department of Defense (DoD) Instrument Approach Procedure (IAP), either high or low altitude, unless a specific request is made by a US military service indicating otherwise. This requirement ensures that military aircraft can operate safely and effectively within the airspace and have the necessary guidelines for navigation and approach. Having a published DoD IAP provides a structured and standardized method for military pilots to execute approaches, especially in adverse weather conditions or when visibility is limited, supporting their operational readiness and safety.

In this context, while other options might suggest alternative scenarios or minimal regulations, the mandate for a published DoD IAP is crucial for safe military operations at civilian airports, thus making it essential for compliance and coordination between military and civilian aviation.