Local employees are nervous but hopeful over news of the merger between Trans World Airlines and American Airlines. It wasn’t entirely a surprise. The company has very few assets–most of its aircraft are leased. And credit watchers last week expressed concern about the amount of cash TWA has on hand for the coming year. Former TWA machinists union local president Keith Nelson hopes American and TWA make a good fit. He’s worried about how changes in ownership will affect the retirement benefits of thousands of retired employees.