overall agility, and data transfer abilities. These problems with key aircraft components, and fleet's high cost, led to calls for its cancellation in 1999. When the requirement for the Apache had been formalised in the early 1990s, military doctrine assumed that a large conventional armoured assault from the Eastern Bloc was Britain's main threat. Following the collapse and break-up of the Soviet Union, the concepts of flexibility and rapid response took precedence. The UK's Strategic Defence Review called for Apaches to undertake amphibious attack missions, operating from the helicopter carrier , the aircraft carriers (all since retired) and their successors, the aircraft carriers, and possibly the amphibious assault vessels and . Each squadron equipped with the Apache should have eight operational aircraft. The Westland Apache experienced delays in entering service due to complications with the modifications made for British service. Prior to the Apache entering service in 2004, several development problems were noted, including a lack of the ability to securely communicate with other helicopters and a risk of damage to the tail rotor and airframe from firing its Hellfire missiles. The problem with using the Hellfire was debris generated by the firing of missiles, both the Hellfire and CRV7 rockets, could strike the body of the aircraft and cause damage; resolving this issue created a delay to training programmes. These problems were corrected prior to entering service, a secure communications suite was installed and Hellfire missiles are routinely fired by Apaches. In 2002, government sources stated that full operational capability was set to be achieved by 2010. In 2005, an out-of-service date for the Apache was forecast at 2030. Various options were considered for maintaining the capability: A capability sustainment programme (CSP) to extend the existing fleet's life to 2040. Buying new Block III helicopters Remanufacturing to AH-64E standard, i.e. putting the existing engines and avionics into new airframes. In August 2015, the UK requested the upgrade of 50 of its Apaches to AH-64E standard through a US Foreign Military Sale. The order was confirmed in 2016, with the contract for remanufacturing of the first 38 awarded in 2017 and the remaining 12 in 2019. Leonardo Helicopters will continue to lead the support the existing Apache AH1s until they are retired from service in 2023–24. The Apache AH1 is to be remanufactured by Boeing to become AH-64E Version 6 aircraft with US engines. Design Several deviations were made to