The merger between Northwest and Delta Airlines was completed on January 31, 2010. Delta is the surviving company.
A few days ago, the folding of Northwest's booking system into Delta's was completed.The Northwest web site now goes to Delta's. All NW and NWA flight codes should now be DL and DAL.
What's interesting is that NWxxxx and NWAxxx flight numbers are still appearing on ACARS and HFDL. According to several people familiar with such things, this might be due to people manually entering codes that they are used to. Since ARINC, which operates both systems, tracks flights by registration number, this should not cause problems.
Something similar is happening with Mode-S identifiers.
Northwest's aircraft are being repainted into Delta livery. Most should be done by now. I'm less sure of what will happen to the old registrations ending in NW.
