This is what Jim Graham said in the March 2nd weekly update:

"Hi everybody, this is Jim Graham with the weekly Flight Operations Update for Friday, March 2nd.* Delta recently announced a voluntary retirement program. We have been asked by some on the line why, unlike the previous two voluntary programs in 2009 and 2011, this program is not being offered to pilots. I want you to know that when the company contemplates any voluntary program, we always consider including all employee groups, including the pilots. Of course one of the primary considerations for including any front-line employees in such a program is the possible negative impact on the operation. Crew Resources and Pilot Scheduling did a thorough analysis of the operational impact should pilots participate in the program. We took a hard look at both the Network plan and our staffing plan going forward. While it is true that we are currently carrying a small surplus of pilots, our staffing plan must take into account unanticipated pilot retirements and the addition of the new 737-900. The result of our analysis was that reducing pilot staffing further at this time would have the potential to negatively impact the operation.* Retirements drive extensive re-training and backfill requirements.* These unique training requirements for Flight Operations and pilots would simply not allow for pilot participation in the current program.* In the end, it was not the right operational decision, nor a decision that would be in the best interest of the entire pilot group at this time. "

For some reason the number "200" comes to mind, but I can't find anything to back it up. "1000" overstaffed doesn't seem like a "small surplus", though.