Wake turbulance. As you are no doubt aware, the rapid expansion post deregulation dried up the available pool of pilots of the normal hiring age . To fill their seats the airlines turned to older pilots some of whom had already suffered through a bankruptcy. Those pilots then, if lucky, made Captain after 10 or 11 years ...lots of them did not. They thus did not have many years with their snout in the trough and when their pension went South they were left with the little they had saved through the years. Let me assure you, the best laid plans mean naught when at age 59 with less than 20 years in the company you are told that your pension will be reduced by 60%.
Water check
Not necessarily. I believe some plans had open and closed years depending on the amount going out of the plan with normal retirements and also dependant on the prevailing interest rates. However I believe Delta did not have this restriction and it would be interesting to see the effect on the Delta pension of so many senior Captains jumping ship prior to Chap 11