Fleet totals (apc data) -

AA 930
DL 841
UA 717

Figure 22 pilots per large w/b. 16 per 767.

Should give approx. how many jobs there are in each category.

With 17% vs 7% large w/b a/c a guy at DL with a seniority number of 700 might have the large w/b bidding power that a UA with 1700 seniority has.
And what flying is done at what base? So the in depth analysis of which airline is 'better' gets tougher. And that's a snapshot of today. Will the differences balance out or are there network reasons for the different fleet groups that might not change.

Another issue is no US airline is buying 767's. What would the fleets percentages look like in 10-15 years when all the 767's have been replaced by 787-8's or larger a/ c??