On 24 June 2018, a Boeing 777-300 was briefly subjected to unexpected and severe Clear Air Turbulence (CAT) whilst level at FL300 which resulted in a serious injury to one of the cabin crew as they cleared up after in-flight service. The Investigation concluded that the turbulence had occurred because of the proximity of the aircraft to a strong jet stream and that the forecast available at pre-flight briefing had underestimated the strength of the associated vertical wind shear.