Originally Posted by prometa

When UA started service to South Africa with the 789, bloggers commented it was going to be flown with a specific subfleet that managed fuel differently. Comments on FT at the time suggested it was computer updates based on learned information about engine envelope given real world data. I would have expected the increased fuel efficiency to be added fleet wide, but earlier this year there was another thread on FT where IAD-CPT went MX and the replacement 789 was delayed after arrival for “software updates”. That suggests the updates aren’t universal. However, my upcoming EWR-CPT flight is on a bird currently scheduled to fly to MUC and NRT between now and then, as well as a domestic SFO-DEN flight. That suggests there isn’t really a subfleet, per se.

Anyone know the implementation details of these particular updates? Will they eventually be fleet wide, or no?