What ADS-B equipment is necessary for aircraft operating in Class A airspace?

In Class A airspace, which generally extends from 18,000 feet up to and including 60,000 feet above sea level, the regulatory requirements for aircraft operation include the necessity for Automatic Dependent Surveillance-Broadcast (ADS-B) equipment. Specifically, the 1090-ES (1090 MHz Extended Squitter) is the equipment mandated for aircraft operating in this airspace.

This type of ADS-B system utilizes the 1090 MHz frequency to broadcast the aircraft's position, velocity, and other relevant data, allowing for enhanced situational awareness and improved traffic management under Instrument Flight Rules (IFR). While 978UAT (Universal Access Transceiver) is another form of ADS-B that operates on a different frequency and is primarily used for aircraft operating below 18,000 feet in Class B and Class C airspace, it is not suitable for use in Class A airspace.

Thus, the necessity of 1090-ES in Class A airspace is rooted in its ability to comply with International Civil Aviation Organization (ICAO) standards and to ensure interoperability with air traffic control systems and other aircraft operating at high altitudes, where the risks and complexities of traffic management are greater.