who determines and at what point how a (larger) airport is configured for operations for the day?

Question

This question is mostly in the context of commercial / scheduled as opposed to GA or other traffic.

It's pretty apparent that "turning around" an airport in the sense of which runways are being used is quite disruptive. If you're somewhere like KDFW, where you have six north-south runways there are possibly dozens (maybe 100+?) aircraft and all the tower/approach/departure ATC folks that are all sort of assuming one of those directions and planning accordingly. My local airport (KRDU) is not remotely close to as busy as a really big airport and has two major parallel runways. Changing the direction of arrivals and departures here is still pretty disruptive.

Obviously if you have some massive wind shift in the middle of the day you're not going to have any choice in the matter, no one wants (or should, or is allowed) to take off with a 25kt tailwind. But on a lot of days, the winds are either light and variable or "light and crosswind" enough that from a purely aeronautical standpoint it might not matter.

In these scenarios (and continuing to use my beloved KRDU), what is the mechanism that people use to figure out whether you're going to be using 5L/5R or 23L/23R?

I can see LOTS of stakeholders here: the local airport, all the airlines, both the local and the larger ATC who has to sequence in arrivals and departures, people on the ground who don't like having their houses flown over, and on and on. But I have to assume there is SOME group of people who at SOME point sit together either literally or figuratively and say "OK, we're going to run runway 23 today, or at least we're going to start with runway 23 and if the winds get beyond [insert some threshold here] we'll flip the field."

Assuming that's reasonably close to correct... who all is part of that group of people? Do they meet in a secret chamber at 0300 each morning to decide this? Do they flip a very fancy aviation-runway-direction coin? Is there some Official Meteorologist Master that provides the official forecast on which these incredibly important decisions are based???

Answer 1

In the usa, the 7110.65 3–5–1 is very very clear:

a. The ATCT supervisor/controller-in-charge (CIC) determines which runway/s are designated RUNWAY IN USE/ACTIVE RUNWAY/DUTY RUNWAY.

b. Assign the runway/s most nearly aligned with the wind when 5 knots or more, or the “calm wind” runway when less than 5 knots unless:

1. Use of another runway is operationally advantageous.
2. A Runway Use Program is in effect.

c. Tailwind and crosswind considerations take precedence over delay/capacity considerations, and noise abatement operations/procedures/agreements.

The wording in the paragraph was changed in the 7110.65Z CHG 3 effective 11/3/2022 (see page BG-6), incorporating N JO 7110.783 which had gone into effect that summer. This was the result of ATSAP Corrective Action Request 2012-009 and NTSB recommendation A-10-109:

Require air traffic control towers to locally develop and implement written runway selection programs that proactively consider current and developing wind conditions and include clearly defined crosswind components, including wind gusts, when considering operational advantage with respect to runway selection.

(Note how even though A-10-109 is specifically cited in the change's background information, the requirement for facilities to define numerical crosswind/gust components did not make it in...)

So the current supervisor in the tower cab—who may or may not be also working a control position at the time—is the final arbiter of which runway should be designated the main runway in use. Pilots are allowed to request the use of other runways and may be accommodated "as soon as is operationally practicable."

At larger airports the tower supervisor can expect much more pushback from the various groups you mentioned, should they choose to change the runway configuration sooner or more often than those groups think is necessary. For example: the airlines know what configuration is most efficient, and will want to use that as long as possible; as a general rule of thumb modern airliners can accept up to a 5-10 knot tailwind if absolutely necessary. The TRACON, meanwhile, will prefer to keep running aircraft in on the original configuration if there is a heavy arrival bank—they would much rather switch when traffic is light. For these reasons, runway changes often lag behind a change in the weather. But different facilities, and different supervisors, will have their own culture and opinion and way of doing things.

There is often a daily telecon among ATC facilities and the airlines for large airports/metroplex areas, and possible configuration changes will be discussed. There are also national telecons throughout the day. But the runway configuration can be changed at any time as weather develops; there is no rule that says "whichever runway is in use at 6AM will remain in use until 6AM tomorrow."

---

When the wind is light, as 3–5–1b specifies, the supervisor will (generally) select the "calm wind" runway. This is a runway that has been designated in the local facility SOP. There can be various justifications for that designation, but the point is to have something which can be referenced as a standard—that way nobody has to flip a coin when there's a direct crosswind at three knots, for example. Or there may be a defined Runway Use Program—for example at LAX they will generally use opposite-direction operations on the midnight shift so that aircraft are both arriving and departing over the water instead of over the city.

Answer 2

randomhead's answer likely applies to most of the airports in the world, but as an example of a somewhat different approach, take EHAM (Amsterdam Schiphol). As a fairly busy airport located right in one of the most densely populated areas of Europe, it is an endless source of noise complaints by the people living in the vicinity, so the airport does not have complete freedom in deciding which runways to use when. Instead, the Government of the Netherlands (its Ministry of Infrastructure) has issued a regulation (IENW/BSK-2023/13636, in Dutch only) defining a strict priority system for allowed runway combinations.

It basically boils down to a set of tables like this one (informal translation mine):

Conditions                | Priority |       Arrivals       |     Departures      |
                          |          |  Primary | Secondary | Primary | Secondary |
-----------------------------------------------------------------------------------
Good visibility, daylight |     1    | RWY 06   | RWY 36R   | RWY 36L | RWY 36C   |
                          |     2    | RWY 18R  | RWY 18C   | RWY 24  | RWY 18L   |
                          |     3    | RWY 06   | RWY 09    | RWY 09  | RWY 36L   |
                          |     4    | RWY 27   | RWY 18R   | RWY 24  | RWY 18L   |
-----------------------------------------------------------------------------------
Good visibility           |     5a   | RWY 36R  | RWY 36C   | RWY 36L | RWY 36C   |
                          |     5b   | RWY 18R  | RWY 18C   | RWY 18L | RWY 18C   |
-----------------------------------------------------------------------------------
Marginal visibility       |     6a   | RWY 36R  | RWY 36C   | RWY 36L | RWY 09    |
                          |     6b   | RWY 18R  | RWY 18C   | RWY 18L | RWY 24    |

The regulation also defines rules for when the secondary runways can be activated (basically, when the capacity of the primary is exhausted in a given period), and when a lower-priority combination can be selected (>15 knots crosswind or >0 knots tailwind on a primary, >20 knots crosswind or >0 knots tailwind on a secondary).

Normally, ATC thus just picks the first usable combination in the table. There are similar tables for night operations and for situations where one of the runways is out of service. The schedule of runway use is normally published roughly half a day in advance based on expected traffic and weather, but exceptional changes can of course be made by ATC when necessary.

So even if the wind was perfect to use 27 for departures and the airlines really wanted that as well, the ATC can't legally do that. That's because arrivals would have to use 24, and its approach path goes right across all of central Amsterdam, mightily annoying a million of voters.