Which aircraft was the first capable of escorting bombers over long distances?

The P-51 Mustang is recognized as the first aircraft specifically designed to escort bombers over long distances. Its design incorporated a powerful engine, excellent range, and high performance at various altitudes, enabling it to accompany heavy bombers during missions deep into enemy territory. The P-51's long-range capabilities significantly enhanced the safety of bomber missions, allowing it to maintain combat air patrols for extended periods, effectively protecting bombers from enemy fighters. The aircraft's aerodynamic efficiency and speed made it a formidable opponent and a crucial asset for the Allied forces during World War II.

In contrast, other aircraft listed, such as the P-40 Warhawk, were used primarily in other roles and lacked the same combination of range and speed that the Mustang offered. The F6F Hellcat, while successful in defeating enemy aircraft, was more focused on carrier-based operations rather than long-range bomber escort. The P-47 Thunderbolt, although also a powerful fighter with good range, was not as optimized for bomber escorting missions as the P-51 Mustang, which ultimately set the standard for long-range escort fighters.