Originally Posted by
MSPeconomist
DL stopped interlining with AA a couple years ago and AFAIK this hasn't changed.
Realistically status and fare class will matter a lot in determining priority for available seats during IROPs, but of course being in the front of the queue (lounge, gate, phone, etc.) will matter a lot too. You're more likely to be rebooked on a codeshare or partner flight than through some other alliance or using one of the ME3 carriers. Sometimes suggesting a creative routing can help, although be careful about visa requirements etc. in some of these circumstances.
DL/AA agreed to a limited interline earlier this year. Basically, passenger must fly between same airports as original ticket (ie. no substituting AUS for SAT) and if there's further IRROPS (ie the flight that you're rebooked onto gets cancelled) all changes/reticketing must be handled by the original airline.