In the trove of documents provided by former National Security Agency contractor Edward Snowden is a treasure. It begins with a riddle: "What do the President of Pakistan, a cigar smuggler, an arms dealer, a counterterrorism target, and a combatting proliferation target have in common? They all used their everyday GSM phone during a flight." This riddle appeared in 2010 in SIDtoday, the internal newsletter of the NSA's Signals Intelligence Directorate, or SID, and it was classified "top secret." It announced the emergence of a new field of espionage that had not yet been explored: the interception of data from phone calls made on board civil aircraft. In a separate internal document from a year earlier, the NSA reported that 50,000 people had already used their mobile phones in flight as of December 2008, a figure that rose to 100,000 by February 2009. In a 2012 presentation, Government Communications Headquarters, or GCHQ ... disclosed a program called "Southwinds," which was used to gather all the cellular activity, voice communication, data, metadata, and content of calls on board commercial aircraft. To spy on a telephone, all that was required was that the aircraft be cruising at an altitude above 10,000 feet. Today, approximately 100 companies permit in-flight use of telephones. This will further extend the scope of espionage by providing a pool of potential targets comprising several hundreds of thousands of people. This implies a population that goes far beyond terrorist targets.