ADS-B In Interval Management

What it does

Interval Management (IM) uses ADS-B In capabilities to precisely manage spacing between aircraft. IM is a component of the future Trajectory Based Operations (TBO) vision, where air traffic controllers may opt to provide IM clearances to flights to manage their spacing intervals relative to other aircraft. Flight-deck applications, like IM, can provide more precise spacing than ground-based decision support tools alone, providing greater TBO benefits.

Interval Management operations involve controllers using automation systems at air traffic facilities, to pre-condition traffic and identify opportunities for IM clearances. A controller then authorizes the flight crew to use the ADS-B In avionics, which provide speed guidance to precisely achieve and maintain an ATC-issued spacing interval (in time or distance) relative to a lead aircraft. The speed guidance is frequently calculated to respond to unexpected behavior by the lead aircraft or wind changes, for example.

ADS-B In Interval Management Avionics

The avionics include cockpit displays that show surrounding traffic for situational awareness and provide speed guidance to help flight crews achieve and maintain an interval from a lead aircraft. IM operations can be used in en route and terminal airspace.


  • Improved arrival throughput through increased delivery accuracy at the TRACON boundary, more consistent arrival spacing, and tighter, more precise spacing during approach operations.
  • Maintaining efficient flight paths during high-density traffic periods.
  • Reduced fuel burn, noise, and emissions when flights stay on their planned Performance Based Navigation (PBN) flight paths.
  • Decreased system delays.


Minimum Operational Performance Standards for IM avionics have been developed jointly with the Radio Technical Commission for Aeronautics (RTCA) and EUROCAE and were finalized in 2020. In 2017, the FAA provided support to NASA's Air Traffic Management (ATM) Technology Demonstration-1 (ATD-1) flight test to evaluate prototype avionics and procedures. In 2019, the FAA sponsored a demonstration of IM operations using prototype avionics on closely spaced parallel runways at San Francisco International Airport. These flight demonstrations have shown precise spacing (within 5-10 seconds of the spacing goal) is possible in real-world environments.

Industry is already starting to use this new technology. Airbus and Boeing are offering new aircraft equipped with ADS-B In. Also, the FAA has partnered with American Airlines and ACSS to certify and install ADS-B In avionics on American Airline's entire fleet of Airbus A321 aircraft. The avionics will enable Initial IM operations, a subset of the full set of operations, in Albuquerque en-route airspace starting in 2022. These operations will continue for one year to gather benefits data that will be shared with the wider community.

The FAA is developing automation requirements and plans to deploy IM operations NAS-wide after 2025.

How it works

Interval Management consists of a set of ground and flight-deck capabilities and procedures that are used in combination by air traffic controllers and flight crews to more efficiently and precisely manage spacing between aircraft in a stream of traffic. During an Interval Management operation, the controller will provide an objective to the flight crew (to achieve and maintain a spacing goal relative to a lead aircraft), and the flight crew will follow the speed guidance provided by the avionics to execute the spacing objective. The avionics and automation systems will support IM operations to the same runway, parallel runways, and crossing & converging runways, enabling increased throughput over today's operations.

Last updated: Tuesday, February 7, 2023