American Airlines (AA), British Airways (BA) and Iberia have kicked off their transatlantic joint venture by announcing four new routes between the US and Europe.
From next year, AA will start flights between New York JFK and Budapest, and Chicago and Helsinki, while BA will start operating between London Heathrow and San Diego.
The fourth route, with Iberia, will be between Madrid and Los Angeles.
The new trilateral relationship officially began today, with the the CEOs of the three Oneworld airlines meeting in London to launch the new routes, all due to start in April 2011.
Gerard Arpey, CEO of AMR Corp, AA's parent company, said: "We have been waiting for 14 years to be able to bring these benefits to our customers and it's great news that we can now put our plans into action."
In addition to the new routes, the trio have announced a series of codeshares.
AA will add its code to 322 BA and Iberia flights to 101 destinations, BA will do the same on 2063 AA and Iberia flights serving 181 destinations, and Iberia will start codesharing on 354 AA and BA flights to 96 destination.
In a joint statement, the airlines said there would be further opportunities to increase codeshares in the future.
Willie Walsh, BA's CEO, said the new routes are an example of how the airlines working together will benefit customers.
"Combined selling and scheduling means that we will be able to operate routes that would not have been viable for us to operate individually," he said.
"This partnership will provide a one-stop shop for transatlantic travel regardless of how you book, which of our airlines you fly with or where you want to transfer."
There has been speculation that BA will take opportunity for expansion offered by Madrid's Barajas airport in its ongoing merger with Iberia, now that a third runway at Heathrow has been vetoed by the UK government.
Antonio Vazquez, chairman and CEO of Iberia, said: "The growth potential of our joint business and the extra capacity Madrid offers will enable Barajas to become one of the main gateways between North America and Europe in the very near future."
All three airlines are members of the Oneworld alliance, which, said AA's Arpey, will benefit: "Our revenue-sharing partnership will further boost Oneworld, in what has been a momentous year for the alliance, and enable us to reduce costs and attract new business."