Me too, but OP might be talking about using the Chase points to book DL (or partner) flights through the Chase portal?

OP: welcome to FT Your question is sort of broad and there are a lot of details that can affect the answer, but as a general guideline:

For airline earning it mostly doesn't matter whether you book directly with the airline or through a third party like a travel agency. As long as your FF# ends up in the reservation somehow you'll get credit.

Also in general, you can credit flights on partner airlines to your DL account. But sometimes the earning rate is different than if it had been a DL-operated flight, and this gets especially confusing with code-shares.

Delta has a chart of how earning works on partner flights that you credit to DL:

https://www.delta.com/content/www/en.../airlines.html

So to sum up, where you book is largely irrelevant. Who operates the flight and how it is marketed (code share etc) is very relevant.

(And if you have a specific flight or alternate flight you're considering, the forum can provide more targeted advice)