Camel and Bucket -
Company's SOP is the Captain decides who the PIC is during his absence. If the experience level is similar it's often becomes the FO almost by default.
Had a flight to S. America where the reserve FO had low experience in the a/c and had never flown the a/c at max gross weight or been to S. America. Gave him the leg but the relief pilot was in charge during my absence.
Others have commented on how crew rest periods are done. At my company typically the PF picks first, then CA(if not PF), then the FO (if not PF), then the relief pilot. If the relief pilot is PF he gets to choose his break. All subject to change if difficult conditions are expected enroute, at which point my break will either be before, or after, the area of concern.
Last edited by misd-agin; 25th May 2011 at 17:35.
Reason: added text for clarity