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When thunderstorms or other severe weather crop up, will the Air Traffic Control in the area proactively route traffic (horizontally or vertically) around the trouble area, or do they leave it up to the individual pilots to request an alternate route?

My intent was asking about commercial aircraft flying IFR, however the information about general aviation and VFR is appreciated

FreeMan
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4 Answers4

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Yes, ATC will reroute flights that are operating on Instrument Flight Rules (IFR).

There are lots of videos of flights getting routed around severe weather floating around on the internet! Atlanta is a great example, as is Memphis, FedEx's hub.

In addition, NASA is working on a product called Dynamic Weather Routes that will help controllers be smarter about amending planned or unplanned weather reroutes.

Sort of, for aircraft operating VFR.

VFR flights that are talking to ATC may get advisories about weather and suggested headings from the controller. I've received notifications about things like 'moderate to heavy precipitation 5-10 miles ahead' many times when operating on VFR flight following.

Community
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egid
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The system is a combination of both. The controller will have a view of the weather radar for the area, and can route traffic around bad areas. They will at least advise the pilots of the bad weather that they can see, and can offer the pilots a deviation or let them know what previous flights have done.

However, the pilots have a better view with the weather radar on their plane, and the pilots have the ultimate decision as to what they will do. The pilots may see a weather return they don't like and ask for deviation around it. Even if ATC denies the request, the pilots are ultimately responsible for the safety of the flight, and should do what they feel is best, even if that means deviating without permission.

There is an interesting article here that is a bit dated, but should still apply to the general idea of how ATC handles bad weather.

fooot
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    Good answer, except maybe it should be made more clear that not all pilots have a weather radar onboard. Large transport aircraft will generally have them, but light aircraft often don't. – reirab Mar 09 '15 at 02:16
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My experience from flying Commercial IFR in Europe is that ATC never proactively re-route around bad weather, but are however usually expedient handling requests from pilots (heading changes to circumnavigate), based on airborne weather radar data.

Waked
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Pilots do not "request routes" except when entering or exiting congested air space, or Class A air space or IFR conditions. They optionally notify ATC of where they might be going by filing a flight plan. VFR pilots can also request flight following. When flight following is activated ATC will notify you of other aircraft or weather conditions that could cross your path.

In uncontrolled airspace, ATC will notify you of a dangerous condition if you are on a flight plan that would bring you into contact with dangerous weather or have flight following activated. It is up to the pilot to decide what to do with that information. In controlled commercial airspace (Class A), ATC will actively route aircraft around dangerous weather conditions.

Tyler Durden
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    I'm not sure I agree with you. When I file an IFR flight plan, I am definitely requesting a route. There's just no promise I will receive that route from the ATC computers. I also can request routes in-flight - GPS direct, different routings, different altitudes - all of these are things I can request from ATC. – egid Mar 05 '15 at 21:03
  • @egid I modified my answer to include class A airspace. – Tyler Durden Mar 05 '15 at 21:10
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    I still disagree with you, even with a mention of Class A. The only airspace in which pilots can operate IFR without a clearance is Class G, and I highly doubt people do it often. In any controlled airspace on an IFR clearance, a pilot can request an amended route from ATC. Like I said - they may not have that request approved, but you can request whatever you like. – egid Mar 05 '15 at 21:13
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    I think the confusion here is that you're talking about VFR flights only, and skipping the IFR side of things. – egid Mar 05 '15 at 21:16
  • @egid My understanding is that a clearance is only required when conditions are IFR. Direct quote from the FAR: "An ATC clearance must be obtained prior to operating within a Class B, Class C, Class D, or Class E surface area when the weather is less than that required for VFR flight." – Tyler Durden Mar 05 '15 at 21:20
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    I can fly VFR, maintaining ≥VFR minimums of a thunderstorm (including beneath one), and be legal but incredibly stupid. I can also be on an IFR clearance and request a route. I'm not sure what you're claiming here. – egid Mar 05 '15 at 21:22
  • @egid I am not claiming anything. I am telling the OP that pilots do not "request routes" unless they are flying in special conditions like Class A or IFR in IFR conditions. I almost never request anything from ATC except flight following sometimes. – Tyler Durden Mar 05 '15 at 21:28
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    If you're operating IFR, you're IFR. There technically isn't even such a thing as "IFR conditions", just IMC. Your "unless" clause is causing your answer to be very incomplete, which is why I'm pushing so hard on this. – egid Mar 05 '15 at 21:31
  • @egid No problem, I don't have an instrument rating so I defer to you and welcome the help. However, my understanding is that if did have a rating and I wanted to fly, say, from Sterling to Laconia and I thought I might run into weather, I could file IFR, but still fly 1200 all the way as long as I encountered no weather. I.e., I don't need to contact Boston Center and get a clearance until I hit weather and activate the IFR plan. My only restriction as far as I know is that if I fly for more than 2 hours I need to call ATC to extend the plan if I am not activating it, so it does not cancel. – Tyler Durden Mar 05 '15 at 21:48
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    At that point, why file? You can get a 'pop up' IFR clearance at any time. That said, why not just fly IFR? You can even go VFR-on-top at that point and you have the best of both worlds. As a CFII I just don't get why, if you think you'd need to go IFR, you wouldn't file from the beginning. Also, as IFR flight plans are from a point A to point B, there's a good chance that you'd have a harder time getting your clearance once you're halfway there. – egid Mar 05 '15 at 21:56
  • This answer would be generally correct if "pilots" were changed to "VFR pilots." And, of course, you can't fly VFR in Class A anyway, so that would also eliminate the need to mention Class A. Also, egid is technically right about "IMC" being the correct term rather than "IFR conditions," though the latter is commonly used, too, even in official National Weather Service forecast products. – reirab Mar 09 '15 at 02:21