The Merlin HC3 entered RAF service with No. 28 Squadron at Benson in January 2001, and the type’s first operational deployment came in Bosnia in 2003. From 2004 RAF Merlins flew in southern Iraq on Operation Telic, where they became the main medical evacuation helicopter around Basra until Britain withdrew in June 2009; two pilots, Flight Lieutenants Kev Harris and Michelle Goodman, received the Distinguished Flying Cross for missions there. To find enough helicopters for Afghanistan, Britain bought six Danish AW101s in 2007 as the Merlin HC3A and formed a second squadron, No. 78.

In 2009 five Merlins were flying troops and supplies in Helmand. The deployment drew criticism because the aircraft initially lacked Kevlar armour, but by July 2010 the fleet was fully protected, and the Merlins allowed the Sea King detachment to leave Afghanistan in 2011. They themselves were withdrawn in June 2013 as British forces drew down. Two years later, at a parade at Benson in July 2015 attended by Prince Michael of Kent, the last of 25 RAF Merlins passed to the Royal Navy’s 845 Naval Air Squadron.

The AW101’s size, three engines and quiet cabin made it attractive as a head-of-state transport, and by 2009 about 15 per cent of sales were VIP aircraft. The highest-profile order came from the United States, where a Lockheed Martin-led team won the competition to replace Marine One with the VH-71 Kestrel. Heavy customisation, cost overruns and political opposition killed the programme in June 2009, and the delivered aircraft were sold to Canada for US$164 million as spares for its CH-149 Cormorants.

India’s order went worse. In February 2010 it signed a US$753 million contract for 12 AW101s to carry the president and prime minister. Allegations that bribes worth almost US$68 million had been paid led India to suspend payments in 2013 and scrap the deal on 1 January 2014 after three aircraft had been delivered; senior Finmeccanica and AgustaWestland executives were tried in Italy, and India’s former air force chief denied wrongdoing. One of the undelivered Indian airframes later turned up in Indonesia, where an air force purchase opposed by the president and the armed forces commander ended with the helicopter sealed in a hangar with police tape in 2017. Indonesian investigators named suspects, a middleman was jailed in 2023, and the helicopter finally entered service in 2024.

The Royal Navy’s Merlin was conceived as an autonomous submarine hunter. The HM1 carried a Blue Kestrel 360-degree search radar, the FLASH dipping sonar, sonobuoys processed by the AQS903 system, derived from the AQS901 of the Nimrod maritime patrol aircraft, and four Sting Ray torpedoes or depth charges. The Merlin Capability Sustainment Programme, reported as costing between £750 million and £1.15 billion, rebuilt 30 aircraft as the HM2 with a new mission system, digital cockpit, electro-optical camera and multi-static sonar processing; the last was delivered in July 2016. Navy Lookout describes a Type 23 frigate’s towed array working with a Merlin as about the best anti-submarine combination available short of another submarine.

The HM2 also carries Crowsnest, a role kit that swaps the sonar suite for a repackaged Thales Searchwater radar and Cerberus mission system to give the Queen Elizabeth-class carriers airborne early warning. It ran about three years late: a limited pre-IOC version sailed with the 2021 carrier group, initial operating capability came in July 2023 and full capability at the end of March 2025, just before three Crowsnest Merlins sailed with HMS Prince of Wales. The Royal Navy plans to retire Crowsnest at the end of 2029.

• PP1–PP9: nine pre-production prototypes, PP1 first flown 9 October 1987.
• Merlin HM1 / HM2: Royal Navy anti-submarine version, 44 built; 30 upgraded to HM2, some fitted for Crowsnest.
• Merlin HC3 / HC3A: RAF transport, 22 new plus six ex-Danish aircraft.
• Merlin HC3i / HC4 / HC4A: interim and full Royal Navy conversions of the 25 HC3/3As with folding rotors and tails and the HM2 cockpit.
• SH-101A, EH-101A, MH-101A: Italian Navy anti-submarine, early warning and amphibious support versions.
• HH-101A Caesar: Italian Air Force combat search and rescue, 15 delivered 2016–2020.
• CH-149 Cormorant: Royal Canadian Air Force search and rescue, with three more and an upgrade ordered in 2022.
• Model 512: Royal Danish Air Force rescue and transport Merlins.
• Models 514–516: Portuguese Air Force rescue, fishery protection and combat rescue Merlins, 12 in all.
• MCH-101 / CH-101: Kawasaki-assembled Japanese mine countermeasures and Antarctic transport versions.
• Model 612 SAR Queen: Norwegian all-weather rescue, 16 ordered.
• Model 614: Polish Navy anti-submarine and combat rescue, four.
• VH-71 Kestrel: cancelled US presidential version.
• VVIP versions: Saudi Arabia, Algeria, Nigeria, Turkmenistan and others.

Large helicopters are maintenance-intensive, and the Merlin is no exception. Navy Lookout reported in 2015 that even with sophisticated self-diagnosis, a Merlin needed about two hours of maintenance for every hour flown and a major overhaul every 600 flying hours, taking around two months; the elderly Sea King ASaC7 it replaced needed ten times as much. With only 30 HM2s, half of them needed for front-line tasks at any time, Britain’s fleet has little slack.

Britain has chosen to upgrade rather than replace: £750 million to £1.15 billion (reports differ) for the HM2, £454 million for the HC4 life sustainment programme, and £269 million for Crowsnest. No operator publishes a reliable cost per flight hour, so the figure in the table is an estimate based on the type’s size, engines and maintenance burden, not an official number.