This has probably been asked before: Which 767/757's are operated on common lines? I'm guessing that crews can switch back and forth between 757 and 767-200/300 series, but not 400 series.(Could do 400 ser. switching, individual cos. likely don't want to do it.) Also, how would pay be handled with companies that have different payscales for 757, and 767, but allow switching between different models?