http://avherald.com/h?article=46679ba1&opt=0
On Nov 25th 2013 Boeing confirmed that a Multi-Operator-Message (MOM) has been sent to B747-8 and B787-800 customers, "who operate some GE-powered engines after instances of ice crystal icing that resulted in temporary diminished engine performance. To reduce chances of ice crystal conditions, Boeing also updated its Airplane Flight Manual (AFM) to prohibit flight within 50 nautical miles of large convective weather systems that may contain ice crystals. Boeing is working with its customers and GE to address the icing issue. Only a small number of GEnx engines have experienced the ice crystal icing issue in flight. GE will introduce the improvements necessary to return the engine to expected performance levels. Boeing is disappointed in any impact this situation may have on our customers, as is the GE team. We, like our customers, expect the delivered product to meet all expectations and will work closely with GE to address the subject condition. We regret the business disruption this will cause for our customer and remain ready to provide whatever assistance we can to Japan Airlines."