There is a very simple process @NWA for changing the FOP on a 012 issued tkt...(orig tkt must have been issued by NW or NWA.COM only)....not agencies/Orbitz etc....

You call the NW agent, they contact their Supervisor who will send an email off along with the new FOP....There is a fee of $50 for this transaction, so you would really need to make it happen....But it definitely is possible and takes about 3 biz days to settle out....

Not all agents are aware, but all they need to do is to make a call to their Supervisor!

Not sure if DL has any similar process, but its doubtful