Knew a dude who operated a bulldozer on contract for the army in the early 60s. He'd get on a bus in Nevada and get taken to "don't ask where." He was given a big bulldozer; which he would use to pile up triangle shaped piles of dirt beside a long, long runway. Then a few days later he'd be back, doing the same thing, the piles he'd made last week mysteriously gone.

Later he found that he was building sound baffles for incoming U2 flights; and the turbulence blew his work away after only a couple landings. Said it was good money and helped him get started. He was eventually one of the bigger military surplus dealers in the USA.