SkyTeam - Online Check-in AF/DL Codeshare

I’m booked on a FRA-JFK AF Ticket, operated by DL (DL07). Does it make any difference whether I check in online with AF or DL regarding customer service in case of delays or cancellations?

Flight is tomorrow, Feb 17th and today’s strike at the airport might be extended to the following day.

You're generally forced to do OLCI with the operating carrier, so even if you start the process on the AF site, it should take you to DL.dumb. Since you're flying ex-EU, you'll be protected under the EU regulations in the case of delays and compensation regardless of whom you check in with. However, you'll probably have to fight DL for compensation harder than you would AF, since DL is only subject to the regulations when operating flights out of the EU.

Thanks i was indeed only able to checkin with Delta. I just hope they can somehow control the situation.