 The US Air Force's HH-53B/C "Super Jolly Green Giant" were for special operations and combat rescue.The Air Force's MH-53H/J/M Pave Low helicopters were the last of the twin-engined H-53s, and were equipped with extensive avionics upgrades for all-weather operation.In October 1967, the U.S. Marine Corps issued a requirement for a helicopter with a lifting capacity 1.8 times that of the CH-53D, that could fit on amphibious assault ships.