ComfortEconomy on KLM AMS-ATL on a DL codeshare for Platinum
 

Oops, meant EconomyComfort

I should know this, and I suspect the answer is no, but are DL Platinums able to upgrade to the EconomyComfort(their version of Comfort+) on KLM metal on a DL code share for free? If so, what time frame?
I have to book an open jaws ticket PBI-BCN, then returning MAD-MSY. My choices are DL metal via CDG, but Comfort+ is sold out, or KLM (on a 787).

You can google it, but I believe that you will be treated the same way as a KLM elite, and you can get a free upgrade to Comfort+.

Economy Comfort is not a separate fare class on KL metal and believe Plats should be able to get it for free (it's discounted for lower status levels). However, if you book a KL-coded, DL-operated flight, you will not be eligible for C+ upgrade until day of departure due to it being a separate fare class on DL metal and upgrade processor will not upgrade a DL Medallion on a KL coded, DL flight (there is no DL SU upgrade class equivalent for KL coded flights).

Thanks!