This paper discusses the distributed nature of airborne software intensive systems. The concept of fly-by-wire, the issues of safety, component communication, and certification are on the forefront of modern airborne applications. Since the communication between variety of on-board systems and subsystems is of paramount importance, the paper discusses the properties of new bus standard based on the Ethernet protocol gaining recognition and widespread use in large commercial aircraft. Avionics Full Duplex Switched Ethernet (AFDX) addresses quality of service, determinism, and reliability required in an aircraft environment. AFDX has reduced the cost of aircraft data networks, increased network capability, and supported determinism required by the airborne system certification guidelines system.