What aircraft serves as the Navy's sole anti-submarine craft?

The P-3C Orion is recognized as the Navy's primary anti-submarine warfare aircraft. This aircraft is specifically designed for patrolling and monitoring maritime areas and is equipped with advanced sensors and weapon systems tailored for detecting and engaging submarines. It utilizes a combination of sonar buoys, magnetic anomaly detection, and advanced radar systems to locate enemy submarines effectively.

The P-3C has a long operational range and endurance, allowing it to conduct lengthy surveillance missions over vast ocean areas, which are crucial in anti-submarine warfare. Its design and equipment make it particularly suited for this role, distinguishing it from other aircraft options listed.

In contrast, the FA/18 Hornet and EA-18G Growler are primarily multi-role fighters with capabilities focused on air-to-air and air-to-ground combat rather than anti-submarine warfare. The E-6B Mercury, while an important communication aircraft, is used mainly for strategic communications and does not fulfill the anti-submarine mission.