The company is mailing customers, travel agents and its 2000 UK staff to tell them that it is adopting a 'business-as-usual' approach while Chapter 11 proceedings are under way. The process will allow United time to restructure.
The airline's loyalty programme, Mileage Plus, has about 40 million members, and it is understood that they will be given regular updates.
A United spokesman said relationships with its marketing services agencies would be unaffected by the bankruptcy proceedings. Fallon currently handles United's advertising business and Zenith handles media. Earlier this year it launched its first European TV campaign since September 11, thought to be worth £10m (Marketing, May 2).
The spokesman denied there would be an integrated campaign using advertising, though industry sources suggested this remained possible.
United's losses are expected to reach $2.5bn (£1.59bn) this year.