At the FlightAware site (http://flightaware.com/live/airport/KIAD) you can view airport activity and see a graph of the activity levels through out a day for any airport. The curves for IAD are different from the other airports I looked at - they have very pronounced peaks while JFK, BWI, LAX, etc. have a much more gradually changing load over 24 hours. Why is that?

I think that one reason for this is, until recently, IAD had a focus on international travel to Europe and transcontinental flights. So you'd see a rush as a bank of of flights arrived from Europe in the morning or left for the West coast and then another rush as the flights left for Europe in the evening or arrived from the West coast.

I think this has been changing as both the international (Asia and Middle East) and domestic focii have been shifting.

JFK and LAX have always had a much wider international focus, while BWI remains mainly domestic.

IAD serves as a large gateway to Europe. To maximize aircraft effeciency, planes leave the US in the early evening, fly overnight to Europe (arriving in the morning) and then turn around and fly back to the US, arriving in the early afternoon. Hence you see a large amount of widebody activity between 3 and 7 pm.

To support those European flights, UA times many of its flights to arrive around 4pm to connect passengers from the US to those European flights. Conversely UA schedules many connecting flights from 5-6 pm so that European psgrs can continue their onward journeys to their final US destinations.

In the morning there are large number of flights heading to Chicago, Denver and various California cities to maximize connections to other cities in the midwest and onwards to Asia.

In summary, while Washington is a hub for UA, it operates slightly differently than ORD or DEN in that as a connection point it serves mainly Europe and (to a lesser extent via UAX) the northeast and so doesn't have as many "banks" of flights during the day.

Every hub has "banks". Banks are when a round of flights from a direction (say the west) all land and about 45 min later (the turn time on these aircraft) the connecting flights going out to the east (in IAD's case, in is a n/s bank, except for the "megabank" which is to Europe.)

This system allows the maximum number of inbound flights to connect with the maximum number of connecting flights with enough time for transfers, but not hours to make the passengers wait.

IAD is unique, becuase historicly, there was no flights to Asia, so the majority of flights fed one rather large bank to Europe. Now that there is Asia service, things have changed a bit, but the concept is still the same.

[QUOTE=fastair;8021366]Every hub has "banks". Banks are when a round of flights from a direction (say the west) all land and about 45 min later (the turn time on these aircraft) the connecting flights going out to the east (in IAD's case, in is a n/s bank, except for the "megabank" which is to Europe.)

This system allows the maximum number of inbound flights to connect with the maximum number of connecting flights with enough time for transfers, but not hours to make the passengers wait.



And, I will add that this is exactly why the GA will attempt to blame delays on "ATC". Never mind the airlines schedule 100 arrivals in an hour when the maximum arrival rate due to airport capacity is 85/hour. Domestic is impacted more of course. The main factor in capacity: Concrete!!

Thanks for the explanation about banking. Are there any other gateway or hub airports that show this concentration of flights? IAD seems unique. From what you all said, I guess the explanation is that it is unique in having such a concentration of Europe bound traffic.

SFO is similar for UA. Most Asia-SFO flights arrive 8am-10am and most SFO-Asia flights depart 11am-2pm (as well as a LHR and FRA flights), so there's a strong concentration of inbound domestic flights during 8am-10am (the single non-stops from ATL/MCO/IAH/YYZ plus others from JFK/BOS/PHL/BWI/DFW) and a strong concentration of outbound ones during the early afternoon. UA has lots of traffic throughout the day as well, of course, but there's the particular blip at the 11am bank.

Moving this to the Washington D.C. forum since it is not UA-specific.

Thanks for your understanding.

iluv2fly
Moderator, UA

It may not be UA-specific, but it is certainly UA-annoying. I'm not claiming other airlines don't have this problem, but UA connections are easily screwed up due to backups at immigration and customs (that is, trying to connect from inbound international to domestic, of course).

In fact it is UA specific and should be moved back to the UA forum. Please allow me to explain.

United Airlines is the *only* airline that is has a real "bank" of flights at IAD. The OP was referring to United's bank operation as well. I spent nearly 9 years working at IAD until 15 months ago and can assure you what I say is true.

Airlines bank flights (at airports); airports don't bank flights.

This thread has much more relevancy to UA fliers than to Washington DC people. It impacts UA fliers in DC and out of DC who use IAD to connect, as well as O & D, so I respectfully request the return of this thread to the United forum.

Thanks,
Jason

I suspect it may all have to do with the large influence of UA.

Two observations;
First, the size of the modulations in the flow of traffic seems much bigger than elsewhere. The chart shows that MOST of the traffic is in these modulation; they are not just small blips on a smooth background as elsewhere.

Second, the peak of the arrivals in these banks is about 1 hour AFTER the departures. Since the banks are about 5 hours apart, this means 4 hours before the next bank. This can not be the connecting flights for international departures can it?

That's why a 4th runway is under construction as we speak. And a 5th runway is in the planning stages.

those curves do not look correct to me. perhaps for flights, but not correct for bodies passing through. shows arrivals boom at 14-1500 and again at 22-2300.

when I look at the enroute/scheduled, I do not see any of the UA or most anyone else arriving from europe or south america in the afternoon.

when the wide bodies start hitting at around 4pm, iad is full for a while.

I think this chart is flights, not passengers, and there is a big difference, since iad has that evening flock of widebodies, while the morning has a lot of rj170, etc putt putting off to columbus, hartford, etc.