(Reuters) - U.S. weapons maker Lockheed Martin Corp is in the final stages of negotiating a deal worth more than $37 billion to sell a record 440 F-35 fighter jets to a group of 11 nations including the United States, two people familiar with the talks said. This would be the biggest deal yet for the stealthy F-35 jet as it is set to make its Paris Airshow debut this week. The sale represents a major shift in sales practices from annual purchases to more economic multi-year deal