On airline hubs

I am writing this post from somewhere over the south-central United States, an hour and a half from landing on a San Francisco to Charlotte flight.  As you might suspect, my final destination is not Charlotte. Nothing against Charlotte – it’s just a hub airport, and so I’m flying through on my way to Pittsburgh.

As I was getting on the plane, a couple passengers whose final destination is Charlotte – and who seemed a bit nervous about flying – asked where I was headed. Pittsburgh, I answered. So why go via Charlotte, they wondered? I commented that I’d booked this flight fairly late, that there aren’t that many SFO-PIT flights, and that it could be worse. I had the option of going via Philadelphia, my hometown. That would have been a flight where I wanted to parachute out of the plane on the way down.

So why have hubs? I spend seven and a quarter hours today from takeoff at SFO to landing at PIT; a nonstop flight would probably be a hair under five. (These are of course not door-to-door times, but the extra time that has to be factored in on either end for ground transportation, security, and so on doesn’t depend on the amount of time I spend in the air.) So the fact that I have to fly via Charlotte costs me, today, somewhere above two hours.

On the other hand, the airline I’m flying (US Airways, if you haven’t guessed from my choices of hub) offers something like a dozen possible routings each day between these two cities. They have no nonstops, but there are a couple possible itineraries each day via each of Charlotte, Philadelphia, and Phoenix, as well as some more complicated ones. So if I called US Airways and said “I’d like to fly from San Francisco to Pittsburgh at [insert time here]”, they could probably accommodate that preference to within an hour or so.

On the other hand, say they didn’t have hubs. Then perhaps US Airways could fill, I don’t know, two planes a day on this route. I’d have to wait around for half a day for my plane!  In the end I spend longer in transit, but less time waiting.

Jarrett Walker, a transit consultant, has written about transfers in designing bus networks. Essentially, if you want to provide a bus from every point to every other point, you can’t provide them very frequently, so people have to wait a long time for their one-seat ride. If you force them to transfer, you can offer more frequent service to some hubs from all the outlying points, so even though people have a two-seat ride the total time spent waiting is less. The same principle applies to air travel.

Finally, my trip today involves a surfeit of coincidences. Had all gone as planned this morning, I would have left my house in Oakland, California, and boarded a BART train that originated in Pittsburg (sic), California to get to the San Francisco airport. After all the flying, I’ll land at the Pittsburgh airport and take a SuperShuttle to my final destination in Oakland, a neighborhood of Pittsburgh.

What are the chances of that?

And what are the chances that on one of the very few times I actually have to cross San Francisco Bay at a certain time, BART trains aren’t running through the Transbay Tube? There was a fire overnight.

Don’t answer those questions.

I’m looking for a job. Despite the peregrinations described in this post, I’m looking in the SF Bay Area. See my LinkedIn profile.

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