Except .84 is a normal cruise speed for the 777 and .80 is a high cost index for the 320 series.

The longest 2 man unaugmented crew flight permissible under 117 is 9 hours. The return flight from GIG to MIA is 8:50 on the 777. That’s all the math you need to know sport.

Anyways I’ve had enough debating a theoretical route on a plane we don’t have or have orders for.