Ah Ham Phisted, that reminds of doing a 3 day MIA, We had pilots paxing with us, One lot of pilots, (can't remember whether it was the operating or paxing pilots) was doing a 4day MIA..
They couldn't explain it to me, when a certain number of flights go to MIA, and the same number fly back to LHR, why you have some paxing..? If you have some paxing west you'll have some paxing east. And it wasn't a different aircraft coming home either..
PS, it wasn't a one-off, it lasted for the quite a while as far as I know.