DL partner who's also partner with TAP
 

Planning to fly NYC-OPO, only availabiluity is on DL JFK-LIS with a short hop to OPO on TAP. Would be nice if I could tack on the LIS-OPO flight as we will have checked luggage and that would save some time.
Not a big deal as there are very cheap flights every hour, but thought I'd ask.
Is there a DL partner who also is partners with TAP, outside of the alliances?
Thanks.

Assuming that DL and TP are interline partners, you could probably piece it together on Expedia or similar to get it all on one ticket so you can check your bags through, etc. That'd be my first stop, anyway.

Sometimes, though, these sorts of tickets can price out much higher than just buying separately - it's hard to say until you actually look into it.

JFK-LIS would be an award on DL (booked on Virgin), LIS-OPO would be cash.
Do DL and TP have an interline agreement? Is there a place to look that up? I can't seem to find it.

TAP is not a DL partner. They won't check through since these are booked on separate reservations (and you won't be able combine them).

https://pro.delta.com/content/agency...e-policy-.html

You can buy a full-fare economy ticket (which is quite expensive) that allows the domestic connection in Europe on TAP.

Otherwise, it looks like you may have to fly via Amsterdam or Paris.

No useful partner -- you'll have to just buy the LIS - OPO flight and leave enough buffer time to re-check (or start your trip in LIS and then go up to OPO a couple days later).

As noted your other alternative is a connection via CDG/AMS -- both AF and KLM fly direct to OPO (although not sure if daily/seasonal/etc) so that would seem to be a good option unless JFK - LIS + LIS - OPO TAP add-on is significantly cheaper

While not required, DL agents i find generally will interline to other airlines. SAT/AUS frequently do it to AY for me.

It's pleasant drive or take the train from Lisbon to Porto. Depending on your plans near Porto and for your entire trip), it could make sense to pick up a rental car at LIS (where you can walk from baggage claim to the rental car area). It's also easy to stay near LIS 9or in the city itself) and do the drive the next day.

And there is also option to use train to travel from Lisbon to Porto. The fastest trains take less than 3 hours. See www.cp.pt for timetables and ticket prices.

The TAP partner with reciprocal benefits would be UA

If you're kind have have status, they will interline your baggage. I had a ticket last summer from LAX-JFK-LHR (DL, VS) and a separate award ticket on BA from LHR to Ibiza. The kind agent at LAX tagged my bags all the way to Ibiza. They can do it.

You certainly can't connect a millage ticket on DL with a cash ticket on TP, but you can get DL and TP on a single cash ticket, they are interline partners, not that this will help the OP. (It also would likely be very expensive since DL doesn't allow interlining on most of its cheaper fares anymore.)

OP is asking if TP and DL have any frequent flyer partners in common—for example, if AF partnered with TAP, OP could issue one ticket with flying blue for both legs.

OP—answer is no, unfortunately.

ITA apparently has a codeshare agreement with TAP. Maybe helpful, maybe not.