DL will not.
Effective for travel on or after January 15, 2013, Delta Air Lines policy will be to check a passenger’s baggage between the origin and destination points that are indicated on a single or conjuncted ticket exclusively. If a second ticket is presented for travel on another airline beyond the destination of the first ticket, the passenger will be advised that Delta will only check the bag to the destination on the first ticket(s). The passenger must collect the baggage at baggage claim for their first ticketed destination, and then re-check their baggage with the down-line carrier for the next flight.
Previously, in cases where a passenger presented more than one ticket to a Delta airport agent at the origination point, Delta would offer to check the baggage from the origin on one Delta ticket to the final destination on the second ticket, collecting both Delta’s and the other airline’s fees. This was done on a courtesy basis but has never been part of an official policy.
The policy update does not apply to interline itineraries, wherein the passenger has an entire journey on one ticket. In these situations, Delta will continue to check baggage through to the ticketed destination as normal policy.