From the Chicago Tribune
Aer Lingus Group PLC plans to start flights between Washington and Madrid next year in partnership with UAL Corp.'s United Airlines.
Seats on the route will be sold by both carriers, and Aer Lingus' aircraft will be used, Chief Executive Dermot Mannion said Thursday in Dublin. There will be joint branding, and the airlines will share the commercial benefits and risk equally. Flights will begin in March 2010.
More like EI is starting a MAD-IAD flight (courtesy of EU membership as well as Open Skies) and UA will code share on it. This will be no different for UA than any other code share arrangement they have.
This may be the shape of things to come, but I would be suprised if they can make this route viable.
I guess this may have been the only route that would not fall a foul of any of their Star Alliance Partners.