Northwest Airlines finally gets access to London Heathrow.

Northwest Airlines is to launch three daily direct flights from Heathrow to Detroit, Minneapolis St. Paul and Seattle in spring 2008. The American airline's joint venture partner KLM Royal Dutch Airlines is freeing up three of its Heathrow slots to make the services possible.

Heathrow Terminal 4 to Minneapolis starts 29 March, taking the place of the Gatwick-Minneapolis route. Heathrow to Detroit starts 1 May, with the Gatwick-Detroit route running in tandem. Both new services use an A330-300, with 34 business class seats and 264 economy. Heathrow to Seattle starts 1 June and uses an A330-200 with 32 business class seats and 211 economy.

The Open Skies agreement between the US and European Union - coming into effect in March 2008 - has opened up competition on transatlantic routes from Heathrow, until now the preserve of just two US carriers, United and American, plus Virgin Atlantic and British Airways.

Northwest-KLM is going head-to-head with BA on the Seattle service, one of its most profitable routes, and with the UK capital accounting for 40% of all transatlantic business class traffic, Heathrow slots are clearly extremely valuable. Delta recently announced a similar joint venture agreement to share three slots at the London hub with Air France.

KLM's flight frequency to its major Amsterdam hub won't be affected by this slot switch to Northwest - the Dutch airline is withdrawing one Rotterdam flight, and shifting two Eindhoven flights to London City airport.