I am a non-pilot who has been listening to various ATC feeds and trying to understand what is going on. I've been able to find surprisingly little information on the various layers that make up the air traffic management system but from listening to SFO atc feeds online, I've come up with the following outline of what radio contacts on a domestic US flight would look like:

  1. ramp control - I know it exists, but have little idea what they do. I would think they manage push back requests, but I hear that on ground frequencies so that cant be strictly correct.

  2. ground control - request pushback, get taxi instructions and hand off to tower when near runway

  3. tower - get takeoff clearance. hand off to departure during climb out

  4. departure - request bearing and altitude, receive vector out of departure airspace in proper direction

  5. center controller (various) - not sure what the relationship is here (pilot requests bearing, altitude, or is it all automated and known to controller) controller maintains separation mins.

  6. approach - there seem to be two stages here? One controller asks for intentions, gives a waypoint and altimeter data. A hand-off is then done to another approach controller who vectors traffic into the pattern for landing, calls base, etc.

  7. tower (arrival) - everything should be all spaced out, so controller just works on fitting departures in. Announce your intention and be granted clearance with initial taxi instructions.

  8. ground (arrival) - get further taxi instructions to gate.

So how accurate is my picture of whats going on? I'd be interested to know exactly how the whole process works from the pilot's perspective. Some specific questions about the process:

  • How automated are aspects? Do controllers ever have information from filed flight plans or is all info passed over radio?
  • Whats the deal with the two approach controllers? (BSR2/MOD2 versus landing)
  • $\begingroup$ One of the ones you are missing is Clearance Delivery for ATC clearances prior to departure. $\endgroup$
    – Ron Beyer
    Sep 15, 2016 at 3:21

1 Answer 1


This is a duplicate question, although this is actually asked much better than the other one is.

Generally, your picture of what goes on is pretty good.

As mentioned in a comment, there is Clearance Delivery, which issues your ATC (IFR) clearance. Except... at most of the larger airports, that function is now automated and the clearance is passed via ACARS, which is essentially a closed e-mail system direct to the aircraft. So it's actually common to NOT talk to Clearance Delivery now in airline operations. You still do at smaller airports that don't have the PDC (Pre-Departure Clearance -- the automation that sends the clearance itself over the ACARS network) installed, and you'll call Clearance if you have a question about how you were cleared, and in a few other uncommon situations such as a reroute that's issued after you got your initial clearance.

Ramp Control exists at some airports, and it's essentially a "ground control" function for a separate, isolated area. So in Atlanta, you actually have several of these, one for Ramp 1, which is the east side of the A terminal and the west side of the B terminal, another for Ramp 2 which is the west B gates and the east C gates, and so on. They control the "in's" and "out's" of their respective ramps, including coordinating who will push back when. As the aircraft leaves the Ramp Control area, it's handed off to Ground Control, and things proceed normally. NOT all airports have this, and not necessarily every terminal (or gate) at a given airport will be controlled by Ramp Control. Gates that aren't controlled by Ramp will typically call Ground to push. SFO is like this.

Typically, controllers see most of what you've filed on your flight plan, so they know before a given flight is passed to them that SkyPig 23 is a 757 that departed JFK, is filed for FL 360, and is going to ATL with a routing of whatever set of airways, points, and STAR. NOT every controller will see everything in the flightplan; I think the TRACON sees remarks but the Center may not, was one example I vaguely remember from a tour a while back. But essentially they know who you are & what you're doing by the time you switch to their frequency. Sometimes things get confused or the pilot requests a change (in altitude, routing, or whatever), and sometimes the controller has to change the plan up, but generally you check in at whatever altitude (and climbing/descending to whatever, if that's the case) and the controller acknowledges and that's that until he has a new clearance (further climb or descent, new routing, approach clearance, etc) to issue.

Mostly now, airlines are filed on both a SID (standard instrument departure) and a STAR (standard terminal arrival route) so "requesting vectors" in pretty uncommon. Could happen if your FMC (flight management computer) dumps your routing, but that's rare, and usually operator error when it does happen. A departure or an arrival might INCLUDE vectors (i.e. fly heading 350, climb & maintain 5000', expect radar vectors to JEBBB), but in those cases it's expected.

Multiple approach controllers are pretty common, especially in the larger terminal areas. Often you'll be switched from Center to one Approach Control frequency, who may be handling all arrivals from the east, with another handling everything from the west. Then as you get close to the airport, they hand you off to "Final", which is still "XYZ Approach" but his job is sequencing everybody onto the base, dogleg, and final, clearing you for the approach, and then handing you off to tower. If the first Approach controller owns airport to 30NM out surface to 17,000', the "Final" controller might own 7000' and below within 12 miles, and Tower owns 3000' and 5 miles. Serious generalization there, but that's the idea... each successive layer of the onion owns a smaller but busier piece of airspace. Letters of Agreement between the Center and the TRACON and then procedures within the TRACON will spell things out in great detail.

Hope that's helpful. Good question asked well; hopefully this won't be lost to memory just because it was asked 2nd.


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