The Sea Knight’s introduction to war was rough. On 15 July 1966, during Operation Hastings, Marine CH-46s collided and were shot down in a landing zone that became known as Helicopter Valley. Within days the whole fleet was grounded while better engine filters were fitted, because sand and debris were destroying engines in as little as 85 hours. Worse followed in 1967, when aircraft began breaking up in flight. On 31 August a CH-46A disintegrated on a medical evacuation flight to USS Tripoli, and when another failed the next day at Marble Mountain the Marines grounded the type except for emergencies, halving their airlift. Investigators from NAVAIR and Boeing Vertol found structural failures around the rear pylon; 80 helicopters were shipped to Futenma on Okinawa, reinforced and returned to service between December 1967 and February 1968.

Boeing’s technical representative John Morgenstern, who arrived at the squadron in 1967, spent much of that period assessing battle damage, counting 53 holes in one aircraft and 46 in another; he went on to support the CH-46 for 47 years. By the end of the war more than a hundred Sea Knights had been lost to enemy fire. On 29 and 30 April 1975 Marine CH-46s and CH-53s flew Operation Frequent Wind, the evacuation of Saigon. The last helicopter to lift off the roof of the US embassy was a CH-46 of HMM-164, and another, “Lady Ace 09” of HMM-165, carried out Ambassador Graham Martin.

The Marines began replacing the CH-46 with the MV-22 Osprey in 2006, squadron by squadron. At its peak, according to the Marine Corps, the community had about 145 Phrogs in 17 squadrons; in the final years of the transition it was down to five squadrons and about 60 aircraft. Pilots were sorry to see it go. “I know it is time for the ‘Phrog’ to retire, but I’m not happy to see it go,” Capt. Brett Bishop of HMM-364 said before the type’s last appearance at the Miramar air show in October 2014.

On 10 April 2015 at Camp Pendleton, HMMT-164, the first active-duty squadron to receive the CH-46A in 1966, became the last to give up the CH-46E, with ten former commanding officers watching. The reserve squadron HMM-774 completed the transition later that year. The final ceremony came on 1 August 2015 at the Smithsonian’s Steven F. Udvar-Hazy Center outside Washington, where CH-46D 153369, freshly repainted in Vietnam-era markings, made the last public appearance of an airworthy Marine Sea Knight. That airframe’s logbook spans Vietnam, where 1st Lt. Joseph Donovan earned the Navy Cross for a rescue under fire in April 1969, Afghanistan in 2004 and Iraq during the surge.

• Vertol 107 and 107-II: prototype of 1958 and the commercial airliner version, first ordered by New York Airways, which flew passengers between Manhattan rooftops and the airports.
• YHC-1A: three evaluation aircraft for the US Army.
• CH-46A: first Marine production model with 1,250 shp T58-GE-8B engines, 17 passengers or 4,000 lb of cargo. UH-46A/D and HH-46A/D: Navy resupply and rescue versions.
• CH-46D: 1,400 shp T58-GE-10 engines and improved rotor blades, 25 troops or 7,000 lb. CH-46F: final production model with revised avionics, 1968–71.
• CH-46E: about 275 A, D and F airframes rebuilt with T58-GE-16 engines, fibreglass blades and stronger structure; later Dynamic Component Upgrade.
• CH-113 Labrador and CH-113A Voyageur: Canadian rescue and army transport versions, 1963–2004.
• Hkp 4A–D: Swedish air force and navy versions, Boeing- and Kawasaki-built, retired in 2011.
• Kawasaki KV-107: Japanese licence production for the Ground, Maritime and Air Self-Defense Forces, Tokyo police, Saudi Arabia and Sweden.

The Sea Knight’s great economic virtue was maturity. By the 2000s Marine maintainers described a supply system so well established that parts were easy to obtain and repairs quick, and the helicopter was simple compared with the tiltrotor that replaced it. No official cost per flight hour was found in the sources opened for this page, so the table gives only a broad estimate for a twin-turbine medium helicopter of its class and age.

The most public price tag came late in its life. The State Department’s Embassy Air operated refurbished, civil-registered CH-46Es, flown and maintained by DynCorp, to keep diplomats off dangerous roads in Afghanistan and Iraq. In fiscal 2017 the CH-46s flew 32,000 scheduled flights plus 3,500 special missions. A September 2019 Inspector General audit found a seven-minute flight from Kabul airport to the embassy cost nearly US$1,500 per seat, an increase of almost 400 percent in four years, because more of the programme’s operating cost was being recovered through ticket prices.