What is a hub airport and why should you want one?

No more blue sky thinking. Image: Getty.

The business lobby wants it. The government wants it. The mayor, Boris Johnson, is just gagging for it. Anyone who is anyone seems determined that London needs a "hub" airport.

And, following this morning’s news that the UK government’s Airports Commission had rejected Johnson’s proposals for a new airport in the Thames Estuary, it seems increasingly likely that one of London's existing airports will be it. This has delighted the big two, and the bosses of both Heathrow ("the only hub left in the race") and Gatwick ("Britain's choice is now clear") are now going around busily explaining why they are the only serious candidate left in the race.

It's clear what these guys get out of it: airports are also businesses, and business want to grow. Why the government or business should be so keen, and what exactly the rest of London gets out of it, perhaps takes some more explaining.

What is a hub?

Let’s start with the science part. "Hub and spoke" is a way of modelling a network in which most journeys go via a few central points. Here's an example:

Image: Elwood64151, via Wikimedia Commons.

There are 15 different airports there. To link them all directly, through “point-to-point” flights, you'd need (quick bit of maths) 120 different routes. But relatively few people want to fly from, say, Albuquerque to Salt Lake City: it’s just not worth an airline’s while to frequently fly the route.

So, instead, a couple of the airports, in this case Denver and LA, are designated “hubs”, which have a disproportionate number of flights routed to them. The outlying airports, which have relatively few, are the “spokes”.

At first glance, this looks like it might be annoying if you happen to be the guy who wants to fly from Albuquerque to Salt Lake City. Actually, though, it might be better even for him. The greater efficiency of the network makes it profitable for the airline to run more frequent planes: the guy might have to change in Denver, but at least he won’t have to wait several days and pay a fortune to make the trip.

Real aviation networks are a bit more complicated than this, of course. And while individual airlines may designate their own, personal hub (Emirates has Dubai, Lufthansa has Frankfurt, etc.), there's no universal definition of the term. It basically just means "big airport with a lot of direct flights". This is the status that Heathrow is determined to maintain.

What are the benefits?

It's obvious why an airport wants to be a hub. It's pretty clear why a hub/spoke model would benefit an airline, too: the greater efficiency makes it possible to replace large numbers of half-empty routes with fewer, fuller ones.

What's more, any airport with spare capacity will be less subject to delays (it’s easier to catch up after problems); and one with large numbers of scheduled flights can offer a wider variety of connections. On the whole, then, a big hub should work better than a small one.

And if you’re not in the aviation industry...?

There are basically three reasons to want to be in the catchment area of a major international hub airport.

1) More destinations. Hub airports, by definition, have more flights to more places. That's good for holiday makers, and good for London's large international population. But it should also be good for...

2) The economy (domestic). London is a major centre for finance, media and several other multinational industries: the more places you can easily get to from London, the more likely companies in those industries are to think it worth setting up shop here. Air freight is also a thing, so this doesn't just apply to services either. There's also...

3) The economy (transient). Any thriving airport is a source of GDP in itself. Even if passengers or freight are only travelling through London, rather than getting off and walking around, that's money that comes into the country that would otherwise be going to Amsterdam or Paris. In other words, the better our air connections, the richer London should be.

So, whether you're a business traveller, or are holidaying on an obscure Pacific island, or just like living in a country with some sort of economy, the hub airport works for you. So we should all be cheering it on, right? Hmm.

What are the downsides?

The arguments in favour of hubs, alas, are not as clear as the aviation industry would like us to think. Many connecting flights are now going via places like Dubai and Doha, which are less out of the way than northwestern Europe: it’s not clear if this will mean a reduction in demand in London and other nearby cities, but it might. New planes such as the Boeing 787 or the Airbus A350 can also do long-haul flights with relatively small number of passengers, making it profitable to fly more point-to-point routes. That could undermine the entire hub/spoke model anyway.

Perhaps most damagingly, some studies suggest that simply increasing the range of destinations on offer doesn’t boost growth at all. What really matters is the number of passengers who actually arrive and leave: being a stopping point for the transient may not benefit the local economy at all.

That’s a problem, because any major airport development will have a pretty nasty downside: noise, air pollution, traffic congestion, all of which will be borne overwhelmingly by those on the flight path or near the airport itself.

This is why decisions about aviation capacity are so incredibly hard. The benefits are widely shared between us; the costs are concentrated among a few. Those few will get angry, and those few can vote.

If you want an explanation for why the Airport Commission won't be releasing its final report until after next year's election, this is it.


Everything you ever wanted to know about the Seoul Metro System but were too afraid to ask

Gwanghwamoon subway station on line 5 in Seoul, 2010. Image: Getty.

Seoul’s metro system carries 7m passengers a day across 1,000 miles of track. The system is as much a regional commuter railway as an urban subway system. Without technically leaving the network, one can travel from Asan over 50 miles to the south of central Seoul, all the way up to the North Korean border 20 miles north of the city.

Fares are incredibly low for a developed country. A basic fare of 1,250 won (about £1) will allow you to travel 10km; it’s only an extra 100 won (about 7p) to travel every additional 5km on most lines.

The trains are reasonably quick: maximum speeds of 62mph and average operating speeds of around 20mph make them comparable to London Underground. But the trains are much more spacious, air conditioned and have wi-fi access. Every station also has protective fences, between platform and track, to prevent suicides and accidents.

The network

The  service has a complex system of ownership and operation. The Seoul Metro Company (owned by Seoul City council) operates lines 5-8 on its own, but lines 1-4 are operated jointly with Korail, the state-owned national rail company. Meanwhile, Line 9 is operated jointly between Trans-Dev (a French company which operates many buses in northern England) and RATP (The Parisian version of TfL).

Then there’s Neotrans, owned by the Korean conglomerate Doosan, which owns and operates the driverless Sinbundang line. The Incheon city government, which borders Seoul to the west, owns and operates Incheon Line 1 and Line 2.

The Airport Express was originally built and owned by a corporation jointly owned by 11 large Korean firms, but is now mostly owned by Korail. The Uijeongbu light railway is currently being taken over by the Uijeongbu city council (that one’s north of Seoul) after the operating company went bankrupt. And the Everline people mover is operated by a joint venture owned by Bombardier and a variety of Korean companies.

Seoul’s subway map. Click to expand. Image: Wikimedia Commons.

The rest of the lines are operated by the national rail operator Korail. The fare structure is either identical or very similar for all of these lines. All buses and trains in the region are accessible with a T-money card, similar to London’s Oyster card. Fares are collected centrally and then distributed back to operators based on levels of usage.


The Korean government spends around £27bn on transport every year: that works out at 10 per cent more per person than the British government spends.  The Seoul subway’s annual loss of around £200m is covered by this budget.

The main reason the loss is much lower than TfL’s £458m is that, despite Seoul’s lower fares, it also has much lower maintenance costs. The oldest line, Line 1 is only 44 years old.

Higher levels of automation and lower crime rates also mean there are fewer staff. Workers pay is also lower: a newly qualified driver will be paid around £27,000 a year compared to £49,000 in London.

New infrastructure is paid for by central government. However, investment in the capital does not cause the same regional rivalries as it does in the UK for a variety of reasons. Firstly, investment is not so heavily concentrated in the capital. Five other cities have subways; the second city of Busan has an extensive five-line network.

What’s more, while investment is still skewed towards Seoul, it’s a much bigger city than London, and South Korea is physically a much smaller country than the UK (about the size of Scotland and Wales combined). Some 40 per cent of the national population lives on the Seoul network – and everyone else who lives on the mainland can be in Seoul within 3 hours.

Finally, politically the biggest divide in South Korea is between the south-west and the south-east (the recently ousted President Park Geun-Hye won just 11 per cent of the vote in the south west, while winning 69 per cent in the south-east). Seoul is seen as neutral territory.  


A driverless train on the Shinbundang Line. Image: Wikicommons.

The system is far from perfect. Seoul’s network is highly radial. It’s incredibly cheap and easy to travel from outer lying areas to the centre, and around the centre itself. But travelling from one of Seoul’s satellite cities to another by public transport is often difficult. A journey from central Goyang (population: 1m) to central Incheon (population: 3m) is around 30 minutes by car. By public transport, it takes around 2 hours. There is no real equivalent of the London Overground.

There is also a lack of fast commuter services. The four-track Seoul Line 1 offers express services to Incheon and Cheonan, and some commuter towns south of the city are covered by intercity services. But most large cities of hundreds of thousands of people within commuting distance (places comparable to Reading or Milton Keynes) are reliant on the subway network, and do not have a fast rail link that takes commuters directly to the city centre.

This is changing however with the construction of a system modelled on the Paris RER and London’s Crossrail. The GTX will operate at maximum speed of 110Mph. The first line (of three planned) is scheduled to open in 2023, and will extend from the new town of Ilsan on the North Korean border to the new town of Dongtan about 25km south of the city centre.

The system will stop much less regularly than Crossrail or the RER resulting in drastic cuts in journey times. For example, the time from llsan to Gangnam (of Gangnam Style fame) will be cut from around 1hr30 to just 17 minutes. When the three-line network is complete most of the major cities in the region will have a direct fast link to Seoul Station, the focal point of the GTX as well as the national rail network. A very good public transport network is going to get even better.