I just came back from a trip on Delta and still do not understand how the Delta boarding process works. From SEA to SLC, I was on a MD90 and was seated about 2/3rds back in coach and was in zone 6. From JFK to SEA the plane was a 737 and I was in the secon to last row but was in zone 4. Can someone please help me understand how Delta determines what rows go into each zone?