Understanding Departure

Most pilots are aware of the general principles of flying under the control of Approach, but what about the other end of RADAR facilities at an airport: Departure?

Contrary to popular belief, Departure is not just a frequency opened to bug you for the first 30 seconds of your flight. It actually works hand-in-hand with Approach to manage the same airspace as the latter.

The primary purpose of Departure as I see it is to ensure that departing planes exit the field’s (RADAR) airspace, which extends to FL180, without interfering either with other departing aircraft or with inbound aircraft, which are very often descending along much the same path by which the departing aircraft are climbing out. (Yes, SIDs/STARs, but we know what percentage of pilots utilize them, so let’s work with what we have for now; in IF)

Before getting into some of the misconceptions, let’s start with basic forms of contact/control:

Check In

Upon departure, if you check in, Departure will give you an initial altitude. Typically FL190 or something else above its airspace.

Thats it.

Check In is complete. You do not need to, nor should you, say or request anything else. You do not need to request altitudes in 3k foot increments. You do not then need to request flight following. I will repeat that.

By checking in, you are asking to fly your flight plan to your destination. You do not then need to ask to fly that flight plan again by requesting flight following.

Check In is not a “hey, how are you” message. It is, itself, an indication that you are now on the RADAR frequency and intend to fly your filed flight plan.

The following requests should not be preceded by Check In. They should be the first message sent to departure.

Radar Vectors

If you request radar vectors, then rather than a simple initial altitude out of the airspace, Departure will guide you out of the airspace and toward your destination.

Once you’ve requested RV, they do not just cancel upon a whim. It is just like Approach. You are required to follow heading and altitude changes. This may mean that you depart by initially turning away from your destination (check out a SID for LAX when westbound runways are in use and destination is to the east; they circle around after going straight out and head northeast via the VOR south of KSMO).

When vectoring you out of the airspace, Departure has to consider both other departures, which may be parallel to you, and inbound aircraft on the approach frequency. Physics doesn’t much care for two bodies occupying the same space at the same time, so be patient. The departure controller knows where Vancouver is in relation to Calgary, but you may have to gain some altitude before traveling over the mountains to the West. Or you may need to avoid a parallel departure to your left…the direction you want to go. You may have to climb high enough to passs over some aircraft descending for landing. The reasons are myriad, but they are reasons.

(Another good example was at LFMN over the weekend. There is terrain just north of the field. So, those that requested RV were first taken south to gain some altitude before being directed north to LSZH. This was not done because I forgot where LSZH was, but because I didn’t want my Departures eating the side of a mountain. However, I lost count of how many of those that asked for RV indicated that they assumed I did just forget where NW was on the compass. Just be patient. There is logic to everything.)

There is no need to say “with you” or anything else. You will get there. You’re looking at a tiny window in front of you. The controller is looking at the entire airspace.

Flight Following

For our purposes, this means you have a flight plan and want to follow it. If granted FF, you may then proceed to do so.

Again, this should be the first thing you say to Departure. If requesting FF, do not Check In first. That’s essentially two requests and unnecessary clutter.

If you are FF, you are responsible for maintaining your own separation. If you decide to ignore ATIS and cut straight through another aircraft, expect a short flight. If heading straight at another aircraft, consider deviating from your flight plan, unless, again, you want your flight cut short for failing to maintain separation.

There are several trends I see with pilots who request FF that are incorrect:

  • Receiving FF does not mean you can instantly tune out. You are still in Departure airspace until FL180. (Besides, it’s never okay to simply change frequency without permission. This is not an exception.)

  • Requesting altitude repeatedly. FF means you’re on your own. Fly your flight plan at the altitude of your discretion. You’re responsible for maintaining separation, but combining FF with requests for intervention from Departure is counter productive and mutually exclusive.

  • Repeatedly requesting frequency change. Again, you are in the airspace until you reach FL180. You do not need to request frequency change every 1k feet of altitude. When you hit FL180, you’ll get the change. (In general, there is really no reason to ever request a frequency change. Controllers do not want more planes on their frequency than they need, so believe me, you’ll get your change. Same with Approach. Same with tower. You don’t need to ask Tower for a freq change as soon as you can slip a sheet of paper between your gear and the runway. They want you off the freq as much as you want off of it, just chill for a second.)

Flying VFR

This is the most overused request of departure, bar none. Flying VFR is generally for GA aircraft flying around without a flight plan. It is not for a 388 with a transatlantic flight plan. You are responsible for maintaining separation with all other aircraft. You should not request altitude changes.

Where I see this misused the most is when it’s used as an attempt to skirt something a pilot has been denied. Generally, at a field where patternwork is being denied, the pilot first requests ILS back to the field. When told that it’s not allowed at the moment, they try the switch to flying VFR and shove my way back in gambit. This is not the purpose of flying VFR.

Another common thing I see on Departure is an aircraft cruising overhead at FL400 to a field 2000 miles away spots an open frequency and tunes in just to request FF. This is unnecessary and just creates needless work for the controller. You are well above their airspace and have no intention of entering it. Interacting with an open frequency just for the sake of it helps no one.

Regarding Granting Altitude Requests

If you request a cruise altitude that is incorrect for your direction of flight, I will reply with one that is correct. This is not an accident on my part, and you do not need to request it again. If your magnetic heading for cruise is between 360 and 179, you will get an odd flight level, whether you request an even one or not, and vice versa. There are flight levels other than FL400, believe it or not.

Also, if you’re flying from KSAN to KLAX, you won’t be given a flight level above 30k feet. It simply makes no sense. People are always screaming about Realism™ on here. You know what the cruise level of the last flight I copied from KLAX-KSAN was? 13k feet. 13k. Not FL310. 13k. Be sensible. If your entire flight path is 90 nm long, you don’t need to climb to the stratosphere.

Returning to the Field

If you change your mind and decide to return to the field, make your request as you would of approach. ILS, visual, RV, etc. once that’s granted, you’ll be handed over to Approach. The approach you’ve been given will show on your tag, you do not need to re-request.

Do not simply switch to Approach (again, never just switch), or request an early frequency change. If you do the latter and are asked of your intentions, the approach is the answer, not the freq change request. Before granting the change, I need to know why, or to whom I’m to hand you off.

In general, I open Departure with my field because departures are in my airspace just as much as inbound aircraft. I don’t ignore departing aircraft the second they’re airborne because there are still 100 ways they can create incursions along the way out.

Most people request FF, and that’s okay, but you still need to be available to the frequency until above FL180. Since IF pilots do not all use SIDs, it can be very hard to predict how they will depart the airspace, but I do pay attention. An incursion on Departure is no less painful than an incursion on Approach. I take them both seriously. The RADAR airspace is controlled airspace, whether you’re inbound or outbound, and taking care to ensure that planes do not collide is something I take seriously. It’s not just to annoy you for a few seconds after departure.


Mr. Tim, I would like to fly a 90 degree left hand turn across the flight path of the overlapping parallel. Is that OK?


Great tutorial! I had no idea!

Yes, sir. NAV overrides all other rules, especially ATIS. (Just in case: I’m being facetious. Please don’t do this.)


Great information. Like a wise individual once said if you fail to plan you plan to fail.



Talking about this I was wondering first
Do pilots have like a NAV mode? Or to elaborate more because it is 99.99% hard to explain that when I fly after takeoff do I follow all the headings the waypoints tell me or Takeoff don’t put heading and wait until they give me something

Too hard it is easier personally

Can the departure controller take over most of the duties of the approach controller if there is none available at the time or what services can it not provide if there is only a twr/grd applicable.

Pilots have a flight plan that they follow with auto pilot which would be the equivalent of NAV, yes.

The difference being that real world pilots use standard departures rather than simply a one-waypoint flight plan to a field 3000 miles away, so you would never see them make a 90 degree turn over the ramp like you do in IF.

As far as asking for a heading goes, that’s up to you. If you check in or request flight following, you can follow your flight plan. But your flight plan should account for other traffic.

This is especially pertinent at fields like KLAX or KATL where there are parallel departures. If you look at the SIDs for these fields, if they’re headed somewhere the opposite direction from takeoff, they still depart a ways out at runway heading before making any turns. They do not simply turn directly across the parallel upwind, which is what many IF pilots do.

So, yes, they may hit the equivalent of NAV early, but their FP would never ignore other traffic or incursion possibilities. They fly standard departures. We aren’t at the point of enforcing those in IF at the moment.


We used to use departure as a second approach for busy hubs, but now we have multiple approaches. Generally, the frequencies should be used for their intended purpose.

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I’ve once received instructions from departure, boy that was fun…a little underrated feature I think :(

Always have admired Tim’s knowledge! Truly one of the leaders in IFATC! Fantastic post Tim!

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Topics like this should be mandatory for people to read through before being allowed to start a flight. It’s frustrating how many people don’t understand even the basic rules of flight. Great tutorial. 👍🏼


When Professor Tim is not teaching at either Harvard or Yale… usually on the same day…he tends to spend his spare time here !


This single, well written, informative post has answered a number questions and queries I’ve had to be honest. Thanks @Tim_B for taking the time to pass on the way things should be done to keep everyone happy 👍🏻

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That’s well said!

Addition: Every pilot has the chance to check flight tracking software like Flightradar24 for departure tracks of current and past flights, even if there are no charts available to the pilot!

Good that you take the time to write detailed advice. However I think an even better way to make people more aware of other traffic is to have a physical collision feature, you hit another plane, there is a physical crash (does not have to be that realistically modelled) both flights are over and IFATC then decides who was at fault through the replay. The culprit is then removed from expert for one week as with ghosting.


So isn’t Check In and Flight Following the same? What’s the difference?

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Yes, a flight following or check in is same. By checking in you want to let the controller know that you have a filed FPL and you’ll be following it. Controller can vector you in case to avoid collision,but then he’ll allow you to continue your FPL once you’re clear of traffic.

Check in is also used if you’re handed over to another radar frequency by the first one. You jus need to check in with other controller once switched to him, he’ll then see your tag and will vector you to the assigned runway.

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Thank you for that!

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What if the approach controller is handling several frequencies and shifts you back and forth between them or between a secondary controller… an example would be KBOS ARTCC and Boston approach freq…do you just check in once…how does an ARTCC freq differ from the standard approach freq !