If a flight is delayed....
 

Why don't they just use another plane? For example. I am sitting in Dulles right now. My flight to RDU is delayed by four hours. We are the last flight out. The entire crew is here ready to go as soon as the plane gets here. I am sure there is some other A319 sitting at a gate that's not going anywhere tonight. Why can't we just use that plane? And then whichever plane we use, uses our plane whenever it gets here in the morning?

Maybe I am just thinking about it to hard. It sounds simple but I am sure there are many factors at hand. Just curious. But it seems so simple to me. Please explain.

Have you got this aircraft rego number?
Have you got the gate number where this aircraft is sitting?
Have you fuelled up this aircraft?

What airline are you flying?

How long would it take to off-load baggage and cargo, transport to the replacement aircraft, and load it?

You're not thinking about it too hard but rather not hard enough. Running an airline is, as you may have read somewhere, not always a profitable business. Overhead costs are high and margins are tight, to keep it short and sweet. Flight planning, the exercise of having aircraft and crews spread across your network so that both of these inputs have as little downtime as possible, and are constantly revenue-producing, is complicated and not helped by delays (mechanical and weather) and other factors which throw of the fine-tuning. No one has aircraft and crews just lying around waiting for something to do. Just think about amplifying your situation to the 100+ airport where your carrier operates.

The real problem, IMHO, is that there are not substantial penalties (in most cases) to airlines for excessive delays, cancellations, etc. Therefore there is no incentive for them to maintain slack in terms of reserve aircraft, crews, etc. The major penalty is the lack in "goodwill" of passengers. However when many people are in locations with one dominant carrier, there is little alternative to switching without major inconvenience.

An analogy (perhaps some will trash). I have a choice of perhaps 3-4 major grocery stores plus a plethora of online sources and specialty markets from which I can choose to buy every week. Therefore to compete, some choose to do so on price, some on quality, some on specialized foods, etc. A store knows that if I come to buy item X there, unless they have inventory they will lose my business for that item (and I can rapidly go elsewhere). However if I book a ticket, lets say PHL - LHR with carrier X, and they cancel a flight, I am stuck with taking the next flight with that carrier and in most circumstances cannot take my money and go to carrier Y.

If a flight is delayed....
 

I'm not sure what your basis for assuming there's another A319 just hanging out. Aircraft utilization is very high. If it made sense to switch you to another aircraft, they would. But it's not like RDU will close before you get there, or any passenger on your plane has a connecting flight out of RDU they might miss. It would be more convenient for you, but airlines make decisions based on their entire operations, not you.

If airlines kept lots of extra planes around as backup (they'd need one of each type of aircraft at each airport they fly out of, since crew is qualified for specific aircraft and each plane seats a different number of passengers), that would be extremely expensive. That cost would be passed on to customers. 8 of 10 passengers would fly on the cheaper airline on the same route who doesn't have backup planes, as history has made clear, customers really only care about price.

I'll go ahead and move this post over to our general travel forum, TravelBuzz.

jackal
Moderator, Information Desk

If it helps the OP find piece of mind....

Every tiny adjustment an airline makes has miles of unintended consequences.

There's a reason you can go on an airline's website and reserve a specific seat on a specific type of plane on a specific flight on a specific date that is ten months in the future. More likely than not, ten months from now the exact type of aircraft with the seating configuration you were shown will show up at the gate at the time the airline said it would.

BUT, there's more to it than that....
Not only will that plane show up, but the hundreds of time-limited parts on that plane will have sufficient service life remaining to complete your flight, as well as all the other flights that are scheduled for that plane. And at the end of the day, that plane's last flight will end at an airport that has all the necessary maintenance personnel, tooling and parts needed that were anticipated ten months ago.
It's not coincidence that one A320 ends its duty day in RDU (a heavy maintenance base), while another ends its duty day in Dayton, where there's no maintenance at all, and yet another ends its day in MIA, where certain specific maintenance items can be completed.
This sort of planning goes into every single aircraft, every single day.
It's mind boggling.

And then we have crew scheduling...but that wasn't my field.
So OP...it's not wanton neglect of you and your fellow passengers. You're looking at the face of a Swiss watch...there's a lot more moving than just the hands.

That other A319 that's sitting there might be scheduled to fly to LAX or SFO the next morning. Weather was pretty bad yesterday - your 4 hour delay was because a flight operated by that A319 you were waiting on was diverted earlier in the day due to weather. So maybe that A319 never makes it to IAD and has to divert elsewhere and weather doesn't clear up for several hours, and the crew has already timed out. Or maybe a mechanical issue comes up that keeps it grounded. Several things could stop it from getting to IAD that night.

This becomes a problem when you consider connecting flights. RDU isn't a hub. No one flying IAD-RDU is connecting elsewhere, at least not on UA. And if they're connecting to another airline on a separate ticket, UA really doesn't care because it's not their responsibility. That other A319 that might be sitting there and might be going to LAX or SFO would likely have some passengers, perhaps several dozen, connecting to points beyond, such as Hawaii or Asia. In the off-chance that they put the RDU flight on that A319 that's already at IAD, then the incoming A319 is diverted and can't make it to IAD, now they have to cancel or delay the LAX/SFO flight and they have to re-accommodate a bunch of passengers who just missed connections. It's easier to just let you guys be a few hours late to RDU because I doubt anyone missed a connection that UA is responsible for. The A319 that's already on the ground is a sure thing for the flight to the west coast hub (well, more of a sure thing than a plane that's not even at the airport yet, things still happen).

I finally made it home at 4 am. I really appreciate everyone's insight. More so with some than others. :) But, let me elaborate. I was flying UA. We literally were the last commercial flight to leave IAD. Yes, I can't confirm that there was another A319 with our seat configuration sitting there, but this has happened to me more than once over the years, at hubs, and I am sure others can concur.

I get this is a delicate dance. But let me elaborate my point just for conversations point.

In my case as I said we were the last commercial flight, the entire crew was already there waiting. We were waiting for our plane to come in. So the hold up wasn't in bound crew or luggage on a plane. I mean maybe a passenger or two was going to RDU from BDL, sure. But again, if another A319 with the same configuration was already at a gate waiting for the next mornings flights to start, why couldn't they just switch everyone/luggage/crew to that gate/plane?

Last week I took the same flight. And our plane had mechanical issues, so they told us we could use the plane coming in from Cancun. So we all switched gates, passanagers/luggage/crew etc.

So how would that be any different? I would highly doubt that at IAD there was no other A319 with our configuration sitting there at the end of a day. And yes, I can't promise that and with all of UAs configurations it could be true that there wasn't. And I don't buy that it's a fuel issue. Wouldn't they have to refuel the plane coming in anyways? Wouldn't the new crew have to do all the same checks regardless of whether the plane was sitting there or just came in?

t325 I just saw your response, after i wrote the above, which I think makes the most sense. Thanks!

As a 20-year 1K UA flyer also plagued by so many of these delays due to "late-arriving aircraft", I empathize with the OP; but also agree with others that often the solution is elusive. Airlines continue to cut capacity and have mothballed aircraft. Some keep a few ready spares at hubs, others don't; and if those spares are used, they're depleted, at least until the next flight cycle (i.e., next day).

Yesterday, I hit the trifecta but was able to benefit from it: each of the last three flights LAX to SFO was delayed one to two+ hours (coming from EWR and ORD) due to upstream mechanicals and crew availability. I was confirmed on the last flight. To avoid another 2 am arrival, I was able to standby on one of the earlier delayed flights, was the first to clear that flight and got to SFO two hours before my ticketed flight would've arrived at SFO. Had the earlier flights not been delayed also, the original delayed flight would've been my only option.

Might have missed it, but I didn't see anyone mention that if there are any passengers on the incoming flight going through to RDU they would be stranded a IAD for the night if another plane was substituted for the last flight out.

As you noted, the airlines can and do swap planes when they feel it makes the most operational sense for them to do so. Just like you, I have no idea if they had overnighting planes at RDU that could have been swapped. If there was one and they didn't use it, the probably have reasons that have already been mentioned upthread, or there are other reasons, such as scheduled maintenance.

Airlines do often switch planes at the last minute in cases like this. I think there is a good chance this was considered, but for some reason it was not possible/preferred by the airline.

While it is tempting to just say, 'airlines don't care, and have no reason to' there are large operations centers that are constantly handling these things and make real efforts to keep things moving smoothly.

Perhaps one of the A319 planes was scheduled for overnight maintenance in RDU. Perhaps your plane needed to be in XXX for maintenance tomorrow evening. There are lots of reasons, including UA deciding it would be more profitable to inconvenience you, my point is that there likely is a reason. I doubt the answer is simply that they nobody bothered to look into a solution.

Close, but not exactly. Seldom do airlines mothball aircraft any more -- they sell them out right to aircraft brokers, other airlines, or dismantellers. Others are simply returned to their lessors. The result is that airlines seldom have any aircraft in storage that can be brought back into the fleet when demand changes.