Dublin based Aer Lingus and Chicago based United Airlines have formally agreed a partnership to codeshare on UA service from Washington Dulles (IAD) to Madrid Barajas Airport.

The cooperation will commence from March 28th.

Aer Lingus itself operates four markets in the US but has recentlly reduced its US schedules as well as deferring delivery of additional long haul aircraft.

Aer Lingus will gain access to the Washington market through the partnership where UA is the leading domestic US operator from the airport with a 74% share of all operated flights. Aer Lingus does currently have an existing partership with Jetblue which is primarily internet based and will direct passengers to each companies respective websites. Jetblue itself operates 103 weekly flights from Washington.

From Madrid, UA will have access to Aer Lingus 9x weekly services to Dublin.