I worked as a contract engineer for a major midwestern manufacturer of big yellow tractors, construction equipment, and engines. At least 80% of the engineers at the location I was at were foriegn nationals on H-1 visas. The majority were Chinese or Indian. Besides making it so American born engineers couldn't get a permanent job with a decent wage, these engineers were working on classified military projects. (We did design work on engines, drivetrains, etc for tracked, wheeled, and "other" vehicles)
These engineers worked here for a few years, then went home taking our technology with them.
The most prominent project we worked on was Crusader, but there were quite a few others, most of them I know I'm not supposed to talk about, and these foriegn nationals had pretty much full access.