Boeing, the world's second-largest aircraft-maker, shut its commercial aircraft manufacturing operations at the weekend after a last-minute effort to agree a new contract with its machinists broke down on Friday night.

Members of the International Association of Machinists and Aerospace Workers - the largest union at Boeing, representing some 27,000 workers - will today take to the picket lines for a third day outside the company's facilities in Washington state, Oregon and Kansas.