FAA has issued airworthiness directive 2021-21-05 for all GEnx-1B64s, -1B64/P1s, -1B64/P2s, -1B67s, -1B67/P1s, -1B67/P2s, -1B70s, -1B70/75/P1s, -1B70/75/P2s, -1B70/P1s, -1B70/P2s, -1B70C/P1s, -1B70C/P2s, -1B74/75/P1s, -1B74/75/P2s, -1B76/P2s, -1B76A/P2s, -2B67s, -2B67/Ps and -2B67Bs, requiring revising the operator's existing FAA-approved minimum equipment list by incorporating into this list the dispatch restrictions listed in this directive, plus initial and repetitive replacement of the electronic engine control MN4 microprocessor, effective Dec. 28, 2021.