SEATTLE - Boeing Co. on Tuesday presented what it called its final contract offer to more than 18,000 Machinists, whose leaders promptly urged the workers to reject the proposal and strike. A top Boeing executive warned that a strike would be devastating. In a statement posted late Tuesday on its Web site, the union said the aerospace giant was insisting on concessions and takeaways in a "corporate strategy to break the workers who have built this company." Union members will vote on the three-year offer Thursday, with the current contract set to expire Friday. "I just cannot emphasize enough what...