G-ZZZE is one of the "odd ones out" with the old in flight entertainment screens that would cost more to upgrade to AVOD. Also GE90 engines although I'm not sure G-ZZZx were the only five like it. I wonder why BA got rid of that one in particular a few years ago (it's been with more than one other airline before being broken up) but maybe it would be more cost-effective to sell the four remaining G-ZZZx and replace them?