Northwest Airlines of the US and KLM, the Dutch subsidiary of Air France-KLM, are starting routes between London Heathrow and three gateway cities in the US, as international airlines move into the main UK hub to intensify competition, in particular with British Airways.

Northwest and KLM, which run their transatlantic operations in a 50/50 joint venture, said yesterday they would launch services next spring between Heathrow and Detroit, Minneapolis/St Paul and Seattle. Until now, BA has had a monopoly of the Heathrow-Seattle route.