Glossary of Traffic Flow Management Terms

When reviewing air traffic information communicated by NBAA Air Traffic Services (ATS) or the FAA, it is common to see acronyms and terms related to Traffic Flow Management (TFM). To assist NBAA Members and the general aviation community, ATS has compiled this glossary.

This glossary is not an all-inclusive aviation glossary. Rather, it is intended to define terms that NBAA ATS uses on a regular basis in communications with NBAA Members and ATS subscribers, or terms that may be found on the FAA’s fly.faa.gov TFM web pages.

Additional aviation terms are available in the FAA’s Glossary of Terms.

1ST TIER

Tier refers to the scope of a TMI. 1ST TIER refers to those enroute centers immediately adjacent to the one where a TMI or a constraint is in place. For example, if there is a 1ST TIER ground stop in place for IAD, which is in Washington Center (ZDC), that would mean that all traffic departing to IAD from ZDC, Boston Center (ZBW), New York Center (ZNY), Cleveland Center (ZOB), Indianapolis Center (ZID), Atlanta Center (ZTL) and Jacksonville Center (ZJX) would be caught in that ground stop and not be allowed to depart until the stop was lifted.
Learn more about Scope

2ND TIER

Tier refers to the scope of a TMI. 2ND TIER refers to those enroute centers immediately adjacent to the one where a TMI or a constraint is in place, plus the centers immediately adjacent to those (meaning a 2ND TIER TMI would capture more traffic than a 1ST TIER TMI). For example, if there is a 2ND TIER ground delay program (GDP) in place at EWR, which is in New York Center (ZNY), that would mean that all traffic departing to EWR from ZNY, Boston Center (ZBW), Cleveland Center (ZOB), Washington Center (ZDC), Indianapolis Center (ZID), Atlanta Center (ZTL), Jacksonville Center (ZJX), Chicago Center (ZAU) and Minneapolis Center (ZMP) would be caught in that GDP and issued EDCTs.
Learn more about Scope

AAR

Acronym for “Airport Acceptance Rate.” The AAR is the number of arrivals an airport is capable of accepting each hour. The AAR can vary depending on weather, construction, equipment outages, etc.

AC, A/C, or ACFT

Various abbreviations that FAA uses for “aircraft.”

Advisory

Advisories are issued by the FAA’s Air Traffic Control System Command Center, whenever they need to communicate important information about the National Airspace System (NAS).
View the Advisories

ADZY or ADVZY

Common abbreviations for “Advisory.”

AFP

Acronym for “Airspace Flow Program.” An AFP is a traffic management initiative (TMI) used to control traffic through a particular section of airspace. Basically, a line (called a Flow Constrained Area or FCA) is drawn on a map, where a constraint, such as thunderstorms, is expected to appear. Any traffic crossing that line is measured and, when the constraint warrants it, the line becomes an AFP. The AFP is a computer program that assigns delays to aircraft in the form of EDCTs. These EDCTS ensure that specific aircraft cross the AFP boundary when there is room for them.
Learn more about AFPs

AR

Abbreviation for “Atlantic Routes.” The ARs are a network of offshore routes along the east coast, commonly used by traffic between the northeast and Florida.

ARPT

Common abbreviation for “airport.”

ARR

Common abbreviation for “arrivals.”

ARTCC

Acronym for “Air Route Traffic Control Center.” These facilities provide air traffic control service to aircraft operating on IFR flight plans within controlled airspace, principally during the enroute phase of flight. Each ARTCC has a traffic management unit (TMU) that interfaces with the Command Center. When equipment capabilities and controller workload permit, certain advisory/assistance services may be provided to VFR aircraft. There are 20 ARTCCs in the continental U.S.

ATC

Acronym for “Air Traffic Control.” A service operated by appropriate authority to promote the safe, orderly and expeditious flow of air traffic.

ATCSCC

Acronym for “Air Traffic Control System Command Center.” The FAA’s ATCSCC oversees the entirety of the National Airspace System (NAS) and is responsible for managing the overall flow of enroute and terminal air traffic. NBAA Air Traffic Services (ATS) works from within the Command Center.

ATCT

Acronym for “Airport Traffic Control Tower.”

C90

Abbreviation for Chicago TRACON.

CDM

Acronym for “Collaborative Decision Making.” CDM is a joint government/industry initiative aimed at improving air traffic flow management through increased information exchange among aviation community stakeholders. CDM is comprised of representatives from government, general aviation, airlines, private industry and academia, who work together to create technological and procedural solutions to the Air Traffic Flow Management (ATFM) challenges faced by the National Airspace System (NAS). CDM can also refer to the letter of agreement and data connection that exists between FAA TFMS and certain “CDM participating” flight plan service providers.

CDR

Acronym for “Coded Departure Routes.” CDRs are predefined and abbreviated departure routes used to minimize the communication required between ATC and air crews – they provide a rapid means of rerouting aircraft when filed routes are constrained by either weather or congestion.

CIGS

Common abbreviation for “ceilings.” Ceilings are the height above the ground of the base of the lowest layer of clouds when over half of the sky is obscured.

CLSD

Abbreviation for “closed.”

Command Center

Refers to the FAA Air Traffic Control System Command Center (ATCSCC). The Command Center oversees the entirety of the National Airspace System (NAS) and is responsible for managing the overall flow of enroute and terminal air traffic. NBAA Air Traffic Services (ATS) works from within the Command Center.

Constraint

A constraint is anything that interferes with the normal flow of air traffic, either in the terminal area, or the enroute area. Common constraints are weather, excess volume, and runway construction.

CTOP

Acronym for “Collaborative Trajectory Options Program.” A CTOP is a traffic management initiative (TMI) that automatically assigns delay or reroutes around one or more FCA-based airspace constraints in order to balance demand with available capacity. A single CTOP can contain multiple FCAs, with each of them functioning like an AFP. Operators are given an opportunity to submit Trajectory Option Sets (TOSs) to express their preferences for which routes they would be willing to fly around the constraints.
Learn more about CTOP

CZV

An abbreviation for the western Canadian centers.

CZY

An abbreviation for the eastern Canadian centers.

DCC

Common abbreviation for the FAA Air Traffic Control System Command Center.

DEP

Common abbreviation for “departures.”

Early Intent

Early intent refers to messages containing flight plan information that are sent directly from a flight plan service provider to FAA’s TFMS up to 24 hours in advance of a flight. Early intent messages allow FAA Air Traffic Managers to know about flight much further in advance than with simple flight plan strip filings, which are only visible to TFMS two to three hours in advance of a flight.

ECFP

Acronym for “Extended Convective Forecast Plot.” The ECFP is an automated weather forecast product, produced by the National Weather Service (NWS), and focused on convective weather. It is similar to the CCFP, but looks further into the future. By looking at the thumbnails provided on the web page, operators can view convective forecasts up to 4 days in the future.
View the ECFP

EDCT

Acronym for “Expect Departure Clearance Time.” An EDCTs is a time issued to a flight to indicate when it can expect to receive departure clearance and are issued in conjunction with delay programs, such as a ground delay programs (GDPs), airspace flow programs (AFPs) and Collaborative Trajectory Options Programs (CTOPs). EDCTs must be adhered to, plus or minus five minutes.

EI

Acronym for “early intent.”

Enroute

The word “enroute” refers to operations that occur in the enroute phase of flight. This is typically considered to be beyond 15 miles from the departure airport and not yet within 15 miles of the destination airport.

FEA/FCA

Acronyms for “Flow Evaluation Area” and “Flow Constrained Area.” Basically, these are lines drawn on a map, where a constraint, such as thunderstorms, is expected to appear. An FEA monitors any traffic crossing that line, while an FCA is the first step in controlling that traffic. FCAs can become airspace flow programs (AFPs) if needed.

Flight Plan

For the purposes of TFM discussions, filing a “flight plan” refers to the operator submitting flight plan information to their flight plan service provider, who in turn sends that information to FAA as early intent and eventually files the actual flight plan strip.

Flight Plan Service Provider

A flight plan service provider is a company that handles certain aspects of flight planning and filing of flight plans on behalf of individual operators.

FPSP

Acronym for “flight plan service provider.”

FSM

Acronym for “Flight Schedule Monitor.” This is a computer application used by FAA Air Traffic Managers and NBAA Air Traffic Management Specialists to monitor air traffic demand.

FYI

Abbreviation for “for your information.” This is almost always used to refer to specific optional reroutes that the Command Center is making available for certain traffic to fly.

GDP

Acronym for “Ground Delay Program.” GDPs are implemented to control air traffic volume to specific airports where the projected traffic demand is expected to exceed the airport’s acceptance rate for a lengthy period of time. This normally happens due to the airport´s acceptance rate being reduced for some reason, such as low ceilings/visibility or runway construction. Flights destined to the affected airport are issued EDCTs at their points of departure. The ECDTs are calculated in such a way as to ensure that traffic arrives at the GDP-controlled airport when there is room for them – ensuring that demand is equal to the airport’s acceptance rate.
Learn more about GDPs

GS

Acronym for “Ground Stop.” Ground Stops are implemented to control air traffic volume to specific airports where the projected traffic demand is expected to exceed the airport’s acceptance rate for a short period of time (for example, when there is a disabled aircraft on a runway). Ground stops are always airport-specific. Flights that are destined to the affected airport are held at their departure point for the duration of the stop. EDCTs are never issued for a ground stop, but an “update time” is provided, indicating when the stop will be cancelled, extended or changed in some other way.
Learn more about Ground Stops

ICR

Acronym for “Integrated Collaborative Rerouting.” ICR is a process that uses FEA/FCAs to identify a constraint early in the day. Traffic managers may issue a planning (PLN) advisory describing the system constraint and providing route guidance. System stakeholders are allowed an opportunity to consider the area of concern, and provide early intent (EI) messages that communicate their decisions in response to the constraint and update TFMS flight trajectories, monitor alert values and routing intentions. At the expiration of the EI window, traffic management can then analyze the customer responses and decide if the actions taken have resolved the issue, or if recommended routes, required routes, AFPs or other TMIs will be necessary to further reduce demand.
Learn more about ICR

Internal

The term “internal” is used within the context of TFM to refer to the scope of a TMI – specifically, those flights departing from within the same enroute center (ARTCC) where a TMI is in place. For example, if there was an internal ground stop in place for DFW, which is in Fort Worth Center (ZFW), that would mean that all flights departing to DFW from within ZFW would be captured in that ground stop and not be allowed to depart until the stop was lifted.

LAADR

Acronym for “Low Altitude Arrival/Departure Routing.” LAADR is typically used to move traffic at lower altitudes when normal routes are impacted by convective weather.

MINIT

Abbreviation for “Minutes in Trail.” MINIT is used to place a specified time interval (for example, 30MINIT) between aircraft along a particular route. This is done to space traffic out to avoid enroute congestion or to meter aircraft to specific airports or terminal areas.

MIT

Acronym for “Miles in Trail.” MIT is used to place a specified distance (for example, 20MIT) between aircraft along a particular route. This is done to space traffic out to avoid enroute congestion or to meter aircraft to specific airports or terminal areas.

MULTI-TAXI

Abbreviation indicating too many aircraft at a particular airport are trying to taxi at once, which can create congestion and departure delays.

N90

Abbreviation for “New York TRACON.”

NAS

Acronym for “National Airspace System.” The NAS refers to the airspace, air navigation facilities, air traffic equipment, air traffic services, airports and landing areas, contained within the United States.

NCT

Abbreviation for “North California TRACON.”

OIS

Acronym for “Operational Information System.” The OIS is an FAA website that provides a high-level, “dashboard” view of the NAS, highlighting delay programs, ground stops, arrival/departure delays and other information.
View the OIS

Ops Plan

Refers to the Strategic Plan of Operation (see SPO).

OTS

Abbreviation for “out of service.”

Q Routes

Q routes are routes that are available for use by RNAV-equipped aircraft operating between 18,000 feet and FL450.

RMD

Abbreviation for “recommended.” This is almost always used to refer to specific reroutes that the Command Center is recommending certain traffic to fly.

RQD

Abbreviation for “required.” This is almost always used to refer to specific reroutes that the Command Center is requiring certain traffic to fly.

RTE

Common abbreviation for “route.”

Scope

Scope defines what aircraft are captured in a particular TMI. For example, if a GDP is used, scope refers to what flights are being impacted by that program and have delays. Scope can be defined by distance (i.e. 1000NM would be flights within 1,000 nautical miles of the constraint), by center (i.e. ZBW+ZNY+ZDC would be flights from within Boston Center, New York Center and Washington Center) or by tier. 1st Tier refers to flights within the enroute centers immediately adjacent to the one where the constraint is (i.e. 1ST TIER for IAD would be flights within ZDC, ZNY, AOB, ZTL and ZJX). 2nd Tier would include all flights within the 1st Tier, plus flights within the centers adjacent to those (further away).
Learn more about Scope

SCT

Abbreviation for “Southern California TRACON.”

SPO

Acronym for “Strategic Plan of Operation.” Also known as the “Ops Plan,” this refers to the daily, continuously updating plan for the how traffic and constraints in the NAS will be managed. This is manifested in the bi-hourly Planning Telcon that is hosted by the Command Center, involving representatives from the air traffic facilities, aircraft operators, and others. The results of the discussion are published immediately after each telcon as an “Operations Plan” Advisory (see Advisories).

STMP

Acronym for “Special Traffic Management Program.” A STMP is a set of special procedures pre-coordinated to manage air traffic for a particular event (such as the Masters Golf Tournament or the Indianapolis 500). Most STMPs simply include a set of required arrival/departure routes, along with event and airport information. Some STMPs also make use of a slot-based reservation system, implemented to regulate arrivals and departures at airports close-by the special events. Slot-based STMPs are no longer used by the FAA for the vast majority of high volume events.
Learn more about STMPs

Structured Routes

The term “structured routes” refers to a pre-coordinated set of routes that air traffic managers will either require or recommend traffic to fly between a particular city pair or between geographic regions. Structured routes may be used instead of allowing operators to fly their preferred routes in order to manage them around a constraint.

SVRWX

Common abbreviation for “severe weather.”

SWAP

Acronym for “Severe Weather Avoidance Plan.” SWAP is an coordinated plan to minimize the effect of severe weather on traffic flows in impacted terminal and/or enroute areas, using a combination of reroutes, delay programs, or other TMIs.

Tactical

The word “tactical” refers to ATC handling an issue apart from the structured plan of operations. For example, a tactical reroute is one that ATC deems necessary to move traffic around a constraint, but which has not necessarily been coordinated with the Command Center. Another example would be when clearance delivery manually (tactically) coordinates an updated EDCT in the event an operator is running late.

TBFM

Acronym for “Time Based Flow Management.” Also known as TMA, this is a mechanism where ATC uses a computer program to accurately meter traffic to a specific runway threshold or to a specific arrival fix. To accomplish this, flights are issued metering delays, which take the form of departure delays or airborne holding. TBFM is used to control traffic from adjacent centers (close-in traffic) only.
Learn more about TBFM

TCF

Acronym for “TFM Convective Forecast.” The TCF is a human-in-the-loop weather forecast product, produced by the National Weather Service (NWS) to focus on convective weather. The TCF is issued year round and is updated every two hours. Each TCF issuance provides graphical thunderstorm forecast information contained in four-, six- and eight-hour panels. The TCF replaced the older Collaborative Convective Forecast Product (CCFP) in March of 2017.
View the TCF

Terminal

The word “terminal” refers to operations that occur in relative close proximity to airports. This is typically considered to be within 15 miles of the departure airport or within 15 miles of the destination airport.

TFM

Acronym for “Traffic Flow Management”. TFM can be defined as the craft of managing traffic in the National Airspace System (NAS), based on capacity and demand. The goal is to collaboratively reduce delay, maximize capacity, increase efficiency, and increase safety throughout the NAS.
Learn more about TFM

TFMS

Acronym for “Traffic Flow Management System.” TFMS is the central computer system that the FAA uses to receive information about planned and active flights; generate forecasts of demand from the current time to several hours ahead; and present this information to air traffic management personnel. TFMS is the system that coordinates and executes TMIs, such as GDPs, ground stops, AFP, etc.

TMI

Acronym for “Traffic Management Initiative.” TMIs are tools that air traffic managers use to manage either enroute or terminal air traffic. TMIs consist of GDPs, ground stops, AFP, TBFM, reroutes, etc.
Learn more about TMIs

TMU

Acronym for “Traffic Management Unit.” A TMU is a team of air traffic managers inside of each enroute center (ARTCC) that focuses on traffic flow management processes (as opposed to separating traffic) and coordinates directly with the Command Center.

TRACON

Abbreviation for “Terminal Radar Control Facility.” A TRACON is a terminal ATC facility that uses radar and non-radar capabilities to provide approach control services to aircraft arriving, departing or transiting airspace in close proximity to a major airport or airport metroplex.

TSD

Acronym for “Traffic Situation Display.” TSD is a software application used by FAA Traffic Managers and NBAA Air Traffic Management Specialists to monitor air traffic, weather and TMIs, along with various overlays to get an overall picture of what is happening in the NAS.

TSTMS

Common abbreviation for “thunderstorms.”

UDP

Acronym for “Unifed Delay Program.” UDP is a methodology used within Ground Delay Programs (GDPs) and Airspace Flow Programs (AFPs) to help ease the workload of traffic managers and make overall delays more equitable. In each hour of the program, empty “slots” are created to allow for pop-up traffic – flights that appear in TFMS after the UDP was issued. However, pop-up flights can face substantial delays, since a UDP will first assign whatever the average delay is for the program before trying to find the next available slot. If a slot is not available for several hours, the delays can become quite lengthy.
Learn more about UDPs

UNKN

Common abbreviation for “unknown.”

VAPS

Abbreviation for “visual approaches.”

VOL

Common abbreviation for “volume.”

VSBY

Common abbreviation for “visibility.”

WX DEV

Common abbreviation for “weather deviation.”

ZAB

Abbreviation for “Albuquerque Center (ARTCC).”

ZAU

Abbreviation for “Chicago Center (ARTCC).”

ZBW

Abbreviation for “Boston Center (ARTCC).”

ZDC

Abbreviation for “Washington Center (ARTCC).”

ZDV

Abbreviation for “Denver Center (ARTCC).”

ZFW

Abbreviation for “Fort Worth Center (ARTCC).”

ZHU

Abbreviation for “Houston Center (ARTCC).”

ZID

Abbreviation for “Indianapolis Center (ARTCC).”

ZJX

Abbreviation for “Jacksonville Center (ARTCC).”

ZKC

Abbreviation for “Kansas City Center (ARTCC).”

ZLA

Abbreviation for “Los Angeles Center (ARTCC).”

ZLC

Abbreviation for “Salt Lake Center (ARTCC).”

ZMA

Abbreviation for “Miami Center (ARTCC).”

ZME

Abbreviation for “Memphis Center (ARTCC).”

ZMP

Abbreviation for “Minneapolis Center (ARTCC).”

ZNY

Abbreviation for “New York Center (ARTCC).”

ZOA

Abbreviation for “Oakland Center (ARTCC).”

ZOB

Abbreviation for “Cleveland Center (ARTCC).”

ZSE

Abbreviation for “Seattle Center (ARTCC).”

ZTL

Abbreviation for “Atlanta Center (ARTCC).”

ZWY

Abbreviation for “New York Oceanic” airspace.