From what I have read, information or remarks from your DL record never are deleted. Not after 2 years, not after 7 years, never. I don't work for Delta, but this is what I have heard?

Other airlines most likely have a similar customer record. However, it seems that at many other carriers, the customer record is only available to the reps at the frequent flyer service center, not to any res/cto/ato/club agent. Further, in these other airline systems, cto/ato/res/club/gate agents cannot just merely enter remarks in a pax permanent record where as at DL they can. Now remarks are entered all the time in a pax reservation (his or her PNR) but not in any kind of record. So the DL difference seems to be the ease at which basically any employee can both read and add things to this permanent file.

I think that UA in the past had a profile where reps could keep this kind of information. There was an article not too long ago where some pax checked in, and was told by a UA csr at the ATO "someone really doesn't like you." This was because of comments in the pax UA account. However, I think that UA has gotten rid of this profile. I have been told by many res agents at UA that all they get is your name/address/tel# and MP status. In the past, they could store seat preference, credit card data, and any remarks that they have entered.

Does anyone have any more information on the practices at other airlines?