ON A CRISP SATURDAY in November 2014, a black Mercedes SUV pulled onto the tarmac of an Austrian specialty aviation company 30 miles south of Vienna. Employees of the firm, Airborne Technologies, which specialized in designing and equipping small aircraft with wireless surveillance platforms, had been ordered to work that weekend because one of the company's investors was scheduled to inspect their latest project.

For four months, Airborne's team had worked nearly nonstop to modify an American-made Thrush 510G crop duster to the exact specifications of an unnamed client. Everything about the project was cloaked in secrecy. The company's executives would refer to the client only as "Echo Papa," and instructed employees to use code words to discuss certain modifications made to the plane. Now the employees would learn that Echo Papa also owned more than a quarter of their company.