Oneworld carriers British Airways, Iberia and American Airlines are to open four new routes next April as part of their new transatlantic joint venture.
American will operate New York JFK-Budapest and Chicago-Helsinki, connecting the US gateways with the bases of Oneworld members Malev and Finnair.
BA will operate London Heathrow-San Diego while Iberia will open Madrid-Los Angeles.
Oneworld disclosed the routes today at an event marking the three-way tie-up in London.
BA chief Willie Walsh describes the venture as "historic", adding: "We've waited 14 years for this."
American is placing its code on 322 BA and Iberia flights, while BA will add its code to 2,063 American and Iberia flights.
Iberia's code will feature on 354 flights operated by BA and American.
"There will be further opportunities to increase codeshares in future," Oneworld adds.