Originally Posted by
Often1
If one wishes to purchase a second or third seat, one must call DL and book those for that purpose. The seats are assigned to a coded name so as to avoid the COC cancellation.
Here are the details:
https://pro.delta.com/content/agency...-comfort-.html
Of note: you do earn Skymiles on the extra seat(s) but you have to manually contact DL to process. However, your extra seat isn't eligible for a comp upgrade!