I flew on a Delta pass I received from a DL employee once. Delta passes receive a certian number of these every year (6?) they can give to their extended family or friends. I had to pay DL $450 for a standby ticket to a destination where fares start at about $1500. For me it was a good deal, but it took me five days to get home. It is only cost effective if you have extra time and have places to stay along the way. I did however get the luxury of AF business class transatlantic on my return.