The ICAO publishes its 18 annexes in English, Arabic, Chinese, French, Russian and Spanish. The annexes represent the standards and recommended practices of the ICAO. Most annexes contain both elements but Annex 2 contains only international standards. Other annexes that contain only standards are Annex 5 -- Units of Measurement, Annex 7 -- Aircraft Nationality and Aircraft Marks and Annex 8 -- Airworthiness of Aircraft. All member states must notify the ICAO if they intend to deviate from the standards found in Annex 2 or any other annex. Each member state retains the right to enact standards that are stricter than those of the ICAO.
Annex 2 consists of five chapters, four appendices and two attachments. Chapter 1 contains a list of definitions for terms used in the annex. For example, "cruising level" means the altitude maintained by an aircraft during a significant portion of its flight. Chapter 2 states the circumstances under which the annex applies; in general, to all aircraft with nationality and registration markings of member states, those countries who have agreed to abide by ICAO's regulations. Chapter 3 lists the general rules. These include such topics as minimum height requirements, cruising levels, right-of-way, landing regulations, flight plans and air traffic control rules. Chapter 4 covers rules for visual flight, clarifying the circumstances under which there is sufficient visibility for such flight, and Chapter 5 covers rules for instrument flight.
Appendix 1 to Annex 2 sets forth the regulations regarding signals. These rules cover the type of signals to use for distress signals along with signals used by aircraft while intercepting and being intercepted. This appendix also lists and illustrates with drawings the hand signals used by ground crews to direct aircraft at airports. Appendix 2 outlines the rules for the interception of aircraft while Appendix 3 lists the tables for cruising levels. Appendix 4 lists the rules for unmanned free balloons.
Attachment A covers the interception of civil aircraft in more detail. Attachment B lists procedures for unlawful interference with civil aircraft. The pilot-in-command is to continue on his flight plan if at all possible and send the proper signals notifying the authorities of the situation.
Annex 2 has been amended more than 30 times since its adoption in the 1940s. These amendments allow the regulations to remain current and deal with emerging issues or make modifications as needed.
