Upgrades JFK to LAX and SFO
DL almost never makes upgrade inventory available on these flights in advance of the day of departure. These are perhaps the best domestic flights DL operates, as they use a 757 equipped with AVOD, and only 16 seats in F, each one a Business Elite recliner.
When you get to JFK, you need to get yourself into a SkyClub ASAP and see if a concierge can get you lined up with an upgrade.