Cockpit voice recordings are not transmitted in real time because of the need to ensure data security. There is a potential for unscrupulous surveillance and interventions, which are capable of compromising the data. There is currently no internationally accepted method available for the encryption of these recordings, although industry-led research is under way.
The limiting factors for the transmission of flight data recordings are the technical and financial challenge of fitting appropriate equipment to the aircraft and the development of the necessary satellite bandwidth.