Simon Calder: This bold move makes perfect sense for airline

Paris and Tokyo make do with two airports; New York has three. Following yesterday's announcement that Southend is to become an easyJet base, London is about to become the world's first fully fledged six-airport city.

Madness, you may conclude. Even though Heathrow has, for decades, been full to bursting, the recent decline in traffic elsewhere means there is space at Gatwick, Luton and Stansted – all of which easyJet already serves.

Yet from the airline's perspective, starting up in south-east Essex makes perfect sense. Budget carriers revel in playing one airport off against another, and Southend must have given easyJet a delicious deal to lure it in on such a scale. At present, you can fly anywhere you like from Southend as long as it is Ireland or Jersey; easyJet's three Airbus jets will expand the departure boards to include our favourite European sun spots.

The airline knows it will cannibalise some of its existing traffic – particularly Stansted travellers from east London and Gatwick passengers from north Kent. But its main purpose is to pursue Billericay man and Brentwood woman. At present Essex residents are most likely to be found flying Ryanair, the dominant airline at Stansted, with British Airways latterly setting up a successful Mediterranean operation from London City. It is no coincidence that the three specific destinations mentioned by easyJet – Barcelona, Faro and Ibiza – are on the route maps of both its rivals.

Travellers from elsewhere in the UK may, though, be baffled. After all, there is general agreement that Britain has too many airports, with Plymouth next for closure. Last year easyJet pulled out of East Midlands because it wasn't making money. In travel terms, the UK is two nations: London and the rest.