Fly offset never used by ATC

Why do ATC never use the possibility to fly offset route when there is a conflict due to tooq many aircrafts ? ATC always use increase or decrease speed or fly a different heading. Flying offset is an easy process in the airbus .

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Hmm… Define “offset route”.

I ask that, because we as ATC have the ability to use whatever means within given regulations to eliminate any conflicts, whether that is speed adjustments, different headings, or altitudes. Not every aircraft has the ability for this “offset route” that you are referencing (which is why I am asking about what it is), especially if doing such a thing takes the aircraft off of the given SID or STAR that they may be on if they are in the Terminal Area.


I’m also curious about this concept of “offset route”…everything you mentioned is easy to do, and is necessary for proper aircraft seperation.

Yes, ATC will tell you to decrease speed sometimes. If you’re on final flying a 747 and you’re following a Cessna 172, they will ask to decrease your speed due to the slower aircraft you’re following. They will also ask you to increase speed for a variety of reasons. If you’re on final in a 172 and there’s a 747 10 miles behind, they might ask you to keep your speed up until maybe a 1 mile final.

Flying different headings is something that happens every day, just like speed restrictions. It can be for so many reasons. They don’t want you on a collision course with crossing traffic. They will either issue a temporary heading change, or an altitude change.

Bottom line is, ATC does this for safe and proper aircraft spacing, just like in the real world. If ATC sees a conflict, they will amend your route accordingly. They can be nice, and routing you around a nasty cumulonimbus cloud with tops of FL400…it can literally be for any reason to maintain safety.

In my mind and as far as I know the offset possibility is used in non-radar airspace like oceanic airsoace or remote areas. I’ve not seen it used elsewhere. Besides that at least in European airspace it is so congested at times, that moving a plane laterally often rises new problems with other aircrafts. In the end they shall all converge at some STAR entry point and at the same altitude constraints, so it is usually better to line up the plane in sequence with the same IAS. Only with very long directs and on the ENR part of the flight could using offset be of value.

in the FMC/MCDU Boeing/Airbus you can select offset of your route right or left by xxNm to avoid a conflicting traffic in front of you. When conflict is over you resume own navigation direct to the next waypoint of your planned route.

thanks gentlemen for your explanations. I was just asking because this possibility OFFSET route exists in the Airbus/ Boeing , is precisely described in the Toliss Airbus aircraft manuals, so I was wondering why it is not used by Vatsim ATC.
I understand fully your explanations and why ATC prefer to use other methods for traffic separation.

I wonder whether ATC anywhere is even allowed to instruct a route offset.

There is no equipment/PBN code that would let them know if an aircraft is able to fly such an offset and it’s by no means a capability that all (or nearly all) aircraft have. To my knowledge, all instances of route offsets have to be initiated by the pilots, either on their own in accordance with special procedures for the airspace (e.g. in at least some oceanic airspaces, as Torben mentioned) or after requesting it and getting approval from ATC (e.g. for weather avoidance).

This is exactly why I was asking. Any such deviation would have to be approved by ATC or given a reason for resolving any conflict as PIC. But by the point anything needs to be done as PIC, ATC should have worked to resolve it.

Additionally, any deviation, including any offset, would take you off of your cleared routing, and require ATC to clear you back onto that route, so any type of offset done by the aircraft would also have to be cleared by ATC.

I can see such an offset being used to deviate around for weather, but for too many aircrafts? That might not be a good use of such a tool, as ATC will still need to resolve the traffic situation, regardless of any such offset.


Hi Patrick,

Flying offset routes is used by controllers on Vatsim.

I have personally experienced this instruction, and I’ve heard it issued to other pilots on frequency. The enroute controller initiated the request to “fly offset x miles right of course”, due to proceeding and trailing traffic congestion. When the conflicting traffic was separated, the controller issued the instruction to resume normal course.

Ok I have never experienced that with Vatsim ATC.

I’ve personally never been offered an offset route by ATC either, but it’s good to know some controllers do use it sometimes based on other replies here. Maybe it just depends on the individual controller and traffic situation. Out of curiosity, what areas do you usually fly in? Wondering if offset routes might be used more in certain higher traffic regions. At any rate, good to keep learning about all the tools available to help with separation. Safe flying out there!

I fly mostly in Europe, from time to time in Americas and Asia.

That’s the beauty of VATSIM - you can fly anywhere in the world. Restricting yourself to your local area is very limiting.

I am not restricting myself to Europe
But time différence and presence of controller are restricting my possibilities to fly in Americas and Asia.