Originally Posted by DAL767-400ER

I was actually surprised to see this change as well, but after searching through Delta's April timetable and listing flights in an Excel sheet, it has become pretty clear that DL is now (finally!) using different codes for all their 767s. Prior this change, you had the code 763 for 767-300s (domestic), 767-300ERs with standard layout, and 767-300ERs with a different layout (6 of them, the former Gulf Air planes). With these new changes, the difference is more obvious:
763 is now just the non-ER 767-300s.
767 is the code for most of their 767-300ERs.
762 is the code for the ex-Gulf Air jets.