Here's a quick stab at showing what seniority levels can hold at Delta (regular line, i.e. block, only) It may not be exact, but is pretty close.
10%- 777capt
20%- 767-400 capt
30%- 767ER capt
40%- 767ER capt
50%- 737-800 capt
60%- MD88 capt, 777f/o
70%- MD88 capt (barely), 767-400f/o
80%- 767ER f/o
90%- 767ER f/o
This is what I got from a quick run through the May 1st category list; if there are any inaccuracies, feel free to correct them.