Flight inspection has been under many names throughout the years, from airway patrol, airway inspection, facility flight check, to flight inspection. A vital part of providing a safe airspace system, the concept is almost as old as the airway system itself, which dates back to the 1920's.
Each country provided or was responsible for providing, flight inspection services for their country. In a few cases, the country would provide these services for its neighboring country. By the late 1940's flight inspection services included flight inspection equipment, airborne flight calibration, avionics support and calibration, and other services necessary to assure the safety of each country's airspace system.
Convention on International Civil Aviation (also known as Chicago Convention), was signed on 7 December 1944 by 52 States. Pending ratification of the Convention by 26 States, the Provisional International Civil Aviation Organization (PICAO) was established. It functioned from 6 June 1945 until 4 April 1947. By 5 March 1947 the 26th ratification was received. ICAO came into being on 4 April 1947.
Airborne inspection of navigational aids is a two-part operation requiring the skills of highly trained flight crews. The first part is an evaluation of the "signal in space", i.e., the radiation signal of the navigational aid, much like that of a radio station. These signals are checked in accordance with the requirements of ICAO. The second part is to certify instrument approach procedures that are constructed to allow pilots to safely use airport runways in adverse weather.
Flight inspection ensures the integrity of instrument approaches and airway procedures that constitute national airspace infrastructures. The ICAO Member States fulfill their requirements through the airborne inspection of all space and ground-based instrument flight procedures and the validation of electronic signals in space.
With the advent of Global Navigation Satellite Systems (GNSS), States now have the ability to implement GNSS procedures without a corresponding ground infrastructure. This technology has made the ICASC education process even more important. The ICASC information sharing process promotes airspace system safety by encouraging competency of flight calibration services worldwide to avoid the indescriminant use of GNSS without the proper certification as required by ICAO.