Originally Posted by
AntonS
For me, VS flight number posts within 5-7 says. DL code share flight number on VS posts 3-5 days.
I can only speak for the DL-marketed/VS-operated version, but 3-5 days is my experience there also.
However, OP will also experience the delay in the LHR-DEL flight, so there's an outside chance that ATL-LHR will post after LHR-DEL is flown, but since it will still post before LHR-DEL, the system will still have time to upgrade OP to DM and apply the extra bonus to LHR-DEL.
I've no idea whether DL's systems are smart enough to figure all that out, but...there's a chance.