Boeing is qualifying the Linux operating system and applications to Level C of DO-178B, even though only Level D is required by FAA, in order to pave the way for Level C applications in the future. A Level D application would be taxi position awareness, which would use GPS data to overlay an aircraft icon (ownship position) on an airport map. The EFB will be interfaced (via ARINC 429 buses) to the navigation system for position, to the inertial reference system for heading, and to the flight management function for origin and destination airport information. Applications to be operationally approved will include aircraft performance calculations and documentation (minimum equipment list, operating manual, airplane flight manual, and en route, approach and departure charts).