Factbox-Seven previous strikes by Boeing's US factory workers

(Reuters) - The International Association of Machinists and Aerospace Workers (IAM) is the largest aerospace union in North America and represents Boeing's U.S. West Coast factory workers.

IAM workers have gone on strike seven times since the Boeing section was established in the 1930s, according to IAM documents.

1948

Workers staged their longest strike, lasting 140 days, over seniority and closed shop issues.

1965

A 19-day strike resulted in improvements to seniority provisions, grievance procedures and dependent medical coverage.

1977

A 45-day strike ended with pension improvements and retiree medical coverage.

1989

A 48-day strike achieved changes to overtime conditions.

1995

A 69-day strike ended with changes to pensions, job security and layoff benefits.

2005

A 28-day strike preserved medical benefits and retiree medical benefits and improved pension benefits and seniority rights.

2008

Workers went on strike for 57 days. The union said it achieved progress on healthcare and pension issues.

(Compiled by Lisa Barrington and Joe Brock; Editing by Jamie Freed and Gerry Doyle)