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6 Ways ATC Controls IFR Traffic Flow For Hundreds Of Aircraft At Once

Here's how ATC manages hundreds of IFR flights into the busiest airports in the country.

1) Published Holding Fixes

When the weather gets bad at a major airport, you'll find aircraft holding at dozens of common fixes on arrival routes surrounding the terminal area. Each aircraft is separated from one another by a few thousand feet vertically, as they hold over a common fix.


2) Standard Instrument Departures (SIDs)

Charted departure procedures are often published to manage heavy traffic areas. They're called "Standard Instrument Departures", but you'll usually hear them called "SIDs." And you can group them into three types.

The First is a radar vector procedure. In a radar vector procedure, ATC gives you vectors to your course. The procedure may give you an altitude to climb to, and provides instructions to follow if you lose your radios as well.

The Second is a standard pilot-navigated procedure using ground based navaids, like VORs and localizers, to help you navigate a course out of the terminal area. With these procedures, you can also fly them with a GPS or RNAV system if they're in your database. The LINDZ 8 in Aspen is a great example of that.

The Third, RNAV procedures, do the same thing as ground navaid based procedures, except they can only be flown by GPS or RNAV systems. And, they use waypoints instead of radials and navaids.

Click here to learn everything you need to know when you hear "Climb via the SID."

3) Standard Terminal Arrivals (STARs)

Arrivals help center and approach control organize traffic flowing into a terminal area. And you don't have to fly a jet to fly an arrival. In the Cirrus, ATC usually assigns an arrival procedure when we return to the Denver area.

STARS usually start with a transition; in this case the TEJAS 3 Arrival starts at the Corpus Christie VOR. But the TEJAS arrival also routes traffic from other areas to the west, like San Antonio. Eventually, all of these transition routes merge, and the aircraft join the same route. On the TEJAS arrival, that happens at GMANN.

Click here to learn everything you need to know when you heard "Descend via the STAR."

4) Expect Departure Clearance Time (EDCT)

An EDCT time is the runway release time for an individual IFR flight. When flow control programs are in use, usually at large airports, ATC may delay your departure to fit you into a slot along with hundreds of other flights. Usually, you cannot depart sooner than an EDCT and have just a few minutes to takeoff before the clearance is void.

Ground Delay Programs are similar, where traffic at originating airports is stopped from taking off. This happens when the destination airport is experiencing significant delays or traffic contraints due to anything from weather to security threats.


5) Standard Taxi Routes

At Dallas/Fort Worth International Airport, there are a series of standard taxi routes to maneuver hundreds of aircraft around one of the largest airports in the country. This removes workload from ground controllers, and makes copying ground clearance instructions simple.

6) Analysis - Airport Arrival Rate (AAR)

The FAA uses a statistic called "Airport Arrival Rates" (AAR) to determine how extensive flow control programs will be. They take into account runway availability, weather conditions, and traffic over a 60 minute period to determine how much traffic can flow into an airport over a given time. The AAR is one tool FAA management uses to determine delays for hundreds of IFR flights.


How else does ATC manage the flow of IFR traffic? Share in the comments below.

Swayne Martin

Swayne is an editor at Boldmethod, certified flight instructor, and an Embraer 145 First Officer for a regional airline. He graduated as an aviation major from the University of North Dakota in 2018, holds a PIC Type Rating for Cessna Citation Jets (CE-525), and is a former pilot for Mokulele Airlines. He's the author of articles, quizzes and lists on Boldmethod every week. You can reach Swayne at, and follow his flying adventures on his YouTube Channel.

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