The Westland-built Sea King has been a mainstay of RAF search and rescue operations for many years, and the sole type used for this role since the Wessex was phased out in the 1990s. The Sea King HAR3 entered RAF service in 1978, and has since been augmented by the improved HAR3A version. Two operational SAR squadrons, Nos 22 and 202, maintain a two-aircraft presence at a total of six locations around the UK, while No 203 (Reserve) Squadron, which is sending a Sea King for the RIAT 2014 static display, at RAF Valley acts as the type's operational conversion unit. The helicopters are kept at 15-minute readiness during daylight hours and 45-minute readiness in darkness. They perform hundreds of call-outs per year as part of their vital life-saving work around the British Isles.