Northwest Airlines Corp., the fourth-largest U.S. airline,...

Northwest Airlines Corp., the fourth-largest U.S. airline, said it reached tentative agreement with its largest union, the Machinists, on new contracts for 18,000 workers. Terms weren’t released. The three collective-bargaining pacts cover clerical workers, customer-service agents, stock clerks, plant protection employees and others. The union plans to vote within days on the contracts, which took more than two years to negotiate.