Ask for the local various PNRs and check your reservation online to check if better seats are available (against payment). Before check-in ask at the airport ticket desk if you can upgrade to PE or similar. Air France and MH are known to do this. I rate the chances for an upgrade on the Delta slim to none. If you have status on any airline try and get it matched on Delta or another Skyteam carrier (only Aerolineas/AR seems to do this).