SFO currently has one of the two main (landing) runways unavailable due to construction, which is not surprisingly causing some delays. Add in weather, and the delays on Thursday afternoon were an average of around 3 hours according to the FAA.

Myself and a number of colleagues were flying back from YVR on Thursday, spread over 2 flights - UA1230 scheduled at 3:00pm, and US2423 scheduled at 7:15pm.

UA1230 ended up being delayed around 6 hours (was due to be closer to 7, but they bought it up a little). The repeated claim from United was that it was due to the runway construction, and it was "beyond our control". As a result, no compensation was offered, and no hotels for those that misconnected (although countless people were proactively moved to other flights - including the 'later' UA2423). The aircraft for this flight had arrived before 2pm, so wasn't the cause of the delay.

UA2423 on the other hand was only delayed by 30 minutes, and that was due to a late arriving aircraft - they were scheduled as on time right up until shortly before departure. This means they departed around 40 minutes before the flight that was scheduled to depart over 4 hours before them.

Now I get it, scheduling is hard and complex, and UA is probably looking at things like connections/etc, but having them say that the delay on UA2423 was "beyond their control" is hiding a significant part of the truth, isn't it? The FAA sets how many flights the airlines can land, but as I understand it, the airline decides which flights will actually get which slot, right?

ie, United actively choose to delay the 3pm flight for far longer than they could have. If nothing else, they could have swapped the slots for the 2 aircraft from YVR, but they made the decision to delay on how much to delay the earlier flight - which in my book isn't "beyond our control".

(Personally I was on the 7:15pm flight, but moved to the 3:00pm flight at around 6pm when I realized it was going to be an easy upgrade for an extra hours worth of sitting in the lounge - so I don't have anything to complain about personally, but several of my colleagues sat at the airport for >6 hours as a result of the delay)

Yes, delays caused by the imposition of restricted landing slots is beyond United's control, regardless of what levers they have within the program.

There's a lot of factors to consider beyond having an airplane, including crew legalities, downstream routing of the aircraft, etc. Also sometimes they expect the program to improve, or end, and it doesn't, or gets worse.

It has been UA's practice when it is restricted by ATC, the unlucky "chosen" is "Beyond UA's control". The nexus for the UA delay was the ATC restriction, You can try to argue UA had the control to select which flight to delay, a Hobson's Choice. With that line of thinking, there will hardly ever be anything out of UA's control except perhaps the airport is closed.

If an airline has a choice of delaying one flight by 8 hours or two flights by 4 hours each, they’ll take the former every time. There are three reasons for this, and you can prioritize them in whichever order you wish: (a) it impacts fewer passengers; (b) in most cases, the marginal impact of a passenger being delayed 4 hours vs 8 hours is less than the marginal impact of being on-time vs delayed 4 hours; and (c) the most common on-time statistic is presented as a percentage, not an average arrival time relative to par.

But WineCountryUA makes a good point; the fact that UA has an input into the matter does not mean that they have control over it.

There were probably many passengers on UA2423 connecting to long haul destinations in the 11pm-midnight bank (SYD/MEL/BNE/AKL/SIN/TPE/MNL/HKG) such that UA would want to prioritize the slot to ensure these passengers make it to their connecting flights, vs UA1230, mostly passengers destined for SFO or connecting to other cities on the west coast that can be more easily accommodated.

I have written more extensively on these processes and the national airspace system management program of the FAA and DOT. Perhaps someone can find some of those discussions and cross-link.

United, and the other SFO airlines, have reduced schedules significantly during construction period. I tried to find a few reference links but they were all coming up with paywalls. The reduced schedules work fairly well when the weather permits but bad weather, as always, has a large impact on even these reduced SFO operations.

When, for whatever reason, an airline can not complete its full schedule it will manage its available resources (airplanes, crews, slots) to minimize the overall impact of the disruption. That means that some flights have minimal delays while others have large delays or are cancelled.

A simple first-in-first-out type approach would not produce a better result as the available resources would not be used as efficiently as possible.

The people who are making these decisions have to sort through large volumes of data, data that often changes after the decisions are make. The data comes from multiple system covering passengers, aircraft requirements, changing weather, crew schedules, legalities, and more. Automation systems are improving and providing those employees with better data to make better decisions. It's far from perfect, but the result is better than if the disruption was not actively managed. I think this is an area where A.I. has the protentional to make significant improvements.

The bottom line is that when an ATC restriction requires a delay or cancellation, whichever flight is ultimately delayed or cancelled will be attributed to the ATC restriction because, without the ATC restriction, the disruption would not have occurred.

This is the FAA's National Airspace System Status website. It is an interesting look into what is going on behind the scenes, particularly the Full Operational Plan page. https://nasstatus.faa.gov/