Over the last century, aviation has evolved to become a driving force for the global economy. In 2006, air transportation produced an estimated $3.5 trillion, nearly 8% of the world gross domestic income . However, air traffic has overwhelmingly increased over the decades, with the number of passengers and amount of cargo transported on worldwide routes reaching an unprecedented 4.4 billion and 85.6 million tons, respectively, in 2006 . Crowded skies combined with factors such as changing business models, terrorist threats, environmental concerns, and passenger needs test the current capacity and capabilities of air transportation systems. Consequently, today the aerospace industry is witnessing a revolutionary trend in commercial aviation, seeking technological and process innovations in aircraft design, manufacturing, operation, maintenance, and traffic management.
Large-scale initiatives are under way to assuredly integrate new aviation technologies into the civil airspace in the next two decades, with an expected threefold increase in airspace capacity. In the United States, the Federal Aviation Administration (FAA) is collaborating with other government agencies, industry, and academia to modernize the current National Airspace System to the Next Generation Air Transportation System.1 Another similar initiative is the Single European Sky ATM Research in Europe.2
A recent vision in commercial aviation is the e-enabled airplane, i.e., an aircraft that can participate as an intelligent node in a global information network . The e-enabled airplane is envisioned to possess advanced avionics highly integrated with wireless commercial technologies for automated functionalities, e.g., global positioning system for navigation , wireless sensors, and radio-frequency identification (RFID) tags for maintenance , . Wireless access points in the in-aircraft network will facilitate communications between onboard systems as well as communications with off-board infrastructure of air traffic control or airlines [aircraft-to-infrastructure communications (A2I)] and another aircraft [aircraft-to-aircraft communications (A2A)]; see Fig. 1. Off-the-shelf and wireless solutions can substantially reduce onboard equipment maintenance overhead as well as system weight , , . This fact and achievable enhancements in information delivery, availability, usage, and management make the e-enabled airplane a promising, cost-effective basis for improvements in flight safety, schedule predictability, maintenance and operational efficiencies, and other areas.
Fig. 1. Illustration of a future air transportation system with e-enabled airplanes, aircraft-to-ground (A2I), and aircraft-to-aircraft communications (A2A).
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The latest developments strongly support the envisioned future of the e-enabled airplane. For instance, next-generation commercial airplanes have wireless access points for receiving loadable software ,  and passive RFID tags for storing maintenance data , . Other examples in commercial aviation include the introduction of 1090 MHz extended squitter data links for A2A/A2I  and broadband networked commercial unmanned aircraft systems .
However, due to the high level of integration with off-the-shelf and wireless technologies, the e-enabled airplane information systems are not completely regulated nor isolated from external network access. New vulnerabilities are introduced that may open access to onboard systems and impede their operation, creating safety and airline business concerns.
Current guidance for airplane airworthiness from aviation regulatory agencies, e.g., , does not cover emerging security threats to the e-enabled airplane , , , . Therefore, to ensure a safe, secure, reliable, and efficient air transportation system with high capacity, security of the e-enabled airplane must be addressed. An important step towards streamlining this effort is to develop a unified framework for identification of security properties that the e-enabled airplane and its applications must satisfy and for evaluation of candidate solutions. This paper provides such a framework, focusing on three representative applications for the operation, maintenance, and control of the e-enabled airplane.
C. E-Enabled Airplane Security Standards and Research
Table 1 presents some security standards for the e-enabled airplane. An Ethernet-based architecture that protects flight-critical in-aircraft network systems from unauthorized access is in . In , this architecture is improved with security mechanisms meeting airline constraints.
Table 1 Most Relevant Standards for the E-Enabled Airplane Security. EDS—Electronic Distribution of Software; AHM—Airplane Health Management; ATC—Air Traffic Control; ADS-B—Automated Dependent Surveillance Broadcast
A well-established guidance for development of loadable software by onboard equipment suppliers is in , defining software safety-criticality levels based on impact of failure on flight safety, i.e., level A to level E with reducing criticality and development effort. Moreover, a data format for secure distribution of loadable software via EDS is in . Recently, safety implications from onboard use of personal devices, e.g., cellular devices and active RFID tags, were studied in . Further, requirements for safe use of passive RFID tags on airplanes are identified in , e.g., use of password-based mechanisms for protecting tag data. Furthermore, ATC tasks based on the ADS-B are presented in .
Research efforts have also begun, focusing on issues not addressed by the above standards. In , , , and , security mechanisms that can strengthen the in-aircraft network architecture are evaluated. In  and , a security framework to analyze a generic EDS system is proposed. Further, in  and , secure integration of wireless sensors and RFID in AHM is studied. In , the potential impact of security solutions on onboard information systems is discussed.
In this paper, we provide an extensive survey of fertile research areas related to the e-enabled airplane, presenting the state-of-the-art and identifying several open problems.