Two points

First, I think Dan/Eric's arguments that the government will force the air force to live within its budget on this buy have already been given some support. When we signed the 2006 Production, Sustainment, and Follow-on Development Memorandum of Understanding (MOU) for the F-35, we did so on the assumption that we would buy 80.  See page 88 of the linked MOA.

Apparently the announcement that we would only buy 65 F-35s came as a surprise to the air force, and this was premised in part on the theory that much of the training could be done in simulators, thus reducing numbers required for pilot training.

However, as the required number has already been downgraded once, how much more room is there to shrink the buy further?

A second issue related to this purchase is the in-house ability to manage the project.  In FYs 07/08-09/10 more than $500M/year in major projects capital money has lapsed, and the figure for FY10/11 is reputed to be ‘north’ of $2B.