Terminal ferocity: Southend's name has angered some / PA

The many faces of 'London'

The Essex resort of Southend has many claims to fame, such as the longest pleasure pier in the world. But in marketing terms, its latest accolade could prove highly valuable. Its airport is now officially classed as "London" by the International Air Transport Association (IATA), even though it is 40 miles from the capital. Good news for the recently refurbished airport – but a rival airport, London City, has attacked the decision. The chief commercial officer, Matthew Hall, called the move "ridiculous and extremely misleading". Read on to discover what's in an airport name.

How are airports classified?

Most of the time there's little argument: the airports of Edinburgh, Bristol, Manchester and so on serve the cities on whose fringes they are located. For the past quarter-century, London has had five IATA-recognised commercial airports: London City is the closest in, followed by Heathrow, with Gatwick, Luton and Stansted lying in the counties beyond. They have now been joined by Southend, a distant 40 miles from the capital. From a marketing perspective, this is great news, because it puts Southend on the map – or rather, on the screen. Henceforth on data displays, which for many travellers are an important part of choosing a flight, "London Southend Airport" will rank alongside Heathrow, Gatwick and London City as a gateway to the capital. As London is by far the world's biggest market for aviation, that is a valuable commercial advantage.

What is London City complaining about?

Bosses of the Docklands facility – the only airport with a London postcode – are annoyed that a small airfield so far from the capital should qualify for inclusion in the London catchment. But Southend is also after some of London City's market – it is well placed for onward travel to Liverpool Street station, with its own railway station about three minutes' walk from passport control. In terms of plane-to-City for passengers with hand baggage only, Southend is about an hour distant, arguably slightly closer than Stansted.

People surely know where Southend is?

Most travellers in Britain do, and anyone seeking a flight to, say, Barcelona will choose the best combination of price, timing and location from the six London airports serving the Catalan capital. But foreigners heading for London may have no idea where each airport is located. A visitor who relies upon global reservations websites could now be offered Southend on the same level as Heathrow, though with rather fewer flights.

What's Southend airport like?

The Essex airport where Freddie Laker began his aviation empire used to rank behind only Heathrow and Manchester in terms of passenger numbers. But in the past few decades its traffic dwindled to almost nothing. Then the Stobart trucking group took over, invested £100m and persuaded easyJet and the Irish airline Aer Arann to move in. Even with the new buildings, it is a small, simple airport with the platform for trains to London practically outside.

So, six London airports – is that it?

Far from it. An airport can apply whatever geographical name it wishes: "London Oxford" currently does so, and "London Manston" near Ramsgate in Kent has in the past, even though they are 60 miles or more from Trafalgar Square. (There is nothing to stop an airport serving more than one city, as Leeds/Bradford and Minneapolis-St Paul have effectively done for decades.)

Southampton and Birmingham, 70 minutes or less from the capital by train have not (yet) added London to their names, but there is nothing to stop them – or the airlines that fly there. Whatever the airport calls itself, an airline can cheerfully (or brazenly) claim that an airports serves a particular city. Even before the IATA ruling, easyJet was classing Southend along with Luton, Gatwick and Stansted as a London airport.

Hasn't Ryanair got some form on this?

Europe's biggest budget airline has been particularly ambitious in its nomenclature. It uses the old US air force base at Hahn in far western Germany, near the Luxembourg border, which is officially classified as "Frankfurt" even though the financial centre is 75 miles away. Even that has been overtaken this summer, though, by "Paris-Vatry-Disney", an airport 93 miles east of the French capital and closer to Belgium than it is to the Eiffel Tower. Sometimes it works in the opposite direction: Ryanair has long flown to Baden-Baden Airpark, an old Canadian air force base outside the lovely German spa town – but insists on calling it Karlsruhe, after the nearest big city.