GCHQ and the NSA have spied on air passengers using in-flight GSM mobile services for years, newly-published documents originally obtained by Edward Snowden reveal.

Technology from UK company AeroMobile and SitaOnAir is used by dozens of airlines to provide in-flight connectivity, including by British Airways, Virgin Atlantic, Lufthansa, and many Arab and Asian companies. Passengers connect to on-board GSM servers, which then communicate with satellites operated by British firm Inmarsat.

“The use of GSM in-flight analysis can help identify the travel of a target—not to mention the other mobile devices (and potentially individuals) onboard the same plane with them,” says a 2010 NSA newsletter.