point8six: so some F/Os (presumably those who are less experienced) are not allowed in the left seat in the cruise while the captain is on rest? Is this the same as the distinction between F/O and S/FO? Or is that just a seniority thing?
One other question: I always thought that decisions to divert to another airport due to crap weather, etc. were solely at the discretion of the captain? Do I infer from some answers on this thread that the airline ops department can have a say too?