Here’s a paragraph from James Fallows’ great piece on the American Military in The Atlantic:

Source locations for parts of the F-35 (more than 90 Congressional districts)

A $10 million parts contract in one congressional district builds one representative’s support. Two $5 million contracts in two districts are twice as good, and better all around would be three contracts at $3 million apiece. Every participant in the military-contracting process understands this logic: the prime contractors who parcel out supply deals around the country, the military’s procurement officers who divide work among contractors, the politicians who vote up or down on the results. In the late 1980s, a coalition of so-called cheap hawks in Congress tried to cut funding for the B-2 bomber. They got nowhere after it became clear that work for the project was being carried out in 46 states and no fewer than 383 congressional districts (of 435 total). The difference between then and now is that in 1989, Northrop, the main contractor for the plane, had to release previously classified data to demonstrate how broadly the dollars were being spread.

More here.