I recently had a situation where I had booked a PNR using the Amex Gold Card $99 Certificate. I moved, and my friend still wanted to fly the same flights, but I would be coming from another location. I originally thought that you couldn't cancel the paid portion (my portion) and still keep the $99 portion. I called DL multiple times, and got the same answer every time. NO! Then I tried another route, asking agents to split the PNR. The first few all said no, so I kept trying the hang up call back route. Finally, an agent split the PNR. I called back again and cancelled my new PNR number. My friends PNR still showed up. He flew the itinerary this weekend. I was a bit worried that he may have issues at check in but nothing happend. I also didn't want to post until after we had both flown.