According to the newspaper, which collaborated with The Intercept website that received a trove of secret documents from Snowden, simply switching on the phone was enough for the intelligence agencies to track it.
NSA or GCHQ would then be able, reportedly, to cross-reference the data with the list of the passengers and even switch off the phone remotely to receive access codes after the device was rebooted.
The intelligent services allegedly intercepted calls on a number of commercial flights, including Russia's Aeroflot's Nice-Moscow flight on May 20, 2011.
The GCHQ reportedly noted that Aeroflot organized a specific system for GSM connections on its aircraft that could be used for legal intercept.
Snowden is currently residing in Russia, where he was granted asylum after fleeing the United States, following his publication of documents on US global surveillance programs.
