What statement accurately describes the listing of military bases in the IFR Enroute Supplement?

The correct answer highlights that access to military bases may require prior coordination. This is crucial for pilots, especially those flying private or non-military aircraft, as military installations often have specific security protocols and airspace restrictions that necessitate prior communication with base authorities before attempting to land or operate in their vicinity.

Military bases are not universally open to civilian aircraft; rather, each facility has its protocols regarding access, which can include requirements for permission or coordination with the appropriate military personnel. This ensures safety, security, and the proper use of military airspace accordingly to regulations and procedures.

In contrast, the other statements do not accurately reflect the reality of operating around military installations. Some bases may indeed allow access under certain conditions, but it is not correct to say they can be used freely or are generally open without restrictions, as this would overlook the necessary coordination and oversight involved. Furthermore, the assertion that military bases are not listed at all is factually incorrect, as they are included in the IFR Enroute Supplement to provide pilots with essential information about available airfields and their operational status.