Seattle ? A tentative four-year settlement was reached Monday night to end a machinists’ strike that has shut down Boeing Co. commercial airplane operations since Sept. 6, union and company spokesmen confirmed.

Boeing and the machinists union said the deal would enhance job security.

Frank Larkin, a spokesman for the International Association of Machinists and Aerospace Workers in Washington, D.C., told The Associated Press the deal was reached shortly before 8 p.m. CDT Monday, in the fifth day of talks at Federal Mediation and Conciliation Service headquarters in Washington and the 52nd day of the walkout.

Boeing spokesman Tim Healy in Seattle said that although he could not give details, the settlement includes varying degrees of change in all three parts of the contract that deal with outsourcing. Other main issues were job security, wages, retirement benefits and medical coverage.

IAM represents about 25,000 workers in and around Seattle, 1,500 in Gresham, Ore., and 750 in Wichita, Kan.