Le Monde and The Intercept report that British and American intelligence agencies have been monitoring cell phone use on commercial flights since 2005.
When you turn your phone on above 10,000 feet, it lets the NSA know your location, according to a leaked 2010 internal newsletter. The newsletter starts with a little riddle demonstrating the scope of the surveillance:
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.
Using secret aerial stations on the ground, Intelligence agencies can intercept signals in “near real time,” allowing them to extract data, including email addresses and Facebook ID data which they could cross reference with flight and passenger data.
These spy programs had cheeky names like “Thieving Magpie” and “Homing Pigeon,” according to Glenn Greenwald in his 2014 book No Place to Hide.
Full article: The NSA Is Spying on Everyone Who Uses Their Phone on a Plane (Inverse)