WASHINGTON -- Lockheed Martin said Friday that incoming CEO Christopher E. Kubasik has resigned because of a "lengthy, close, personal relationship with a subordinate employee."Marillyn A. Hewson, who was in line to become president and chief operating officer, will become the first female chief executive of the giant defense contractor on Jan. 1.The revelation brings Kubasik's term as CEO to a close before it even started. Previously Lockheed's chief operating officer and president, Kubasik had been preparing for a Jan. 1 handoff of the company's reins from CEO Robert J. Stevens.A Lockheed employee since 1999, he had been groomed for the chief executive job, serving previously as chief financial officer and heading the contractor's electronic systems business.In a call with reporters Friday, Stevens, who is also Lockheed's chairman, said an employee notified officials in October. Lockheed hired an outside firm to investigate, before asking Kubasik to resign."I'm deeply disappointed and genuinely saddened by Chris's actions," Stevens said. "We have a code of ethics and business conduct in our company that applies to every person, and having a close personal relationship with a subordinate employee clearly violates that code of conduct."The shake-up comes at a difficult time for the world's largest defense contractor, which has been trying to rapidly reposition itself in response to a slowdown in federal spending. In recent years, Lockheed has laid off employees, bought out top executives and consolidated facilities to slim down.The company said the relationship will not affect the company's operations or finances.Calls to Kubasik's home were not returned. Stevens, who provided limited details about the relationship, said the employee involved no longer works for Lockheed.Lockheed's board had a special meeting Friday, where, Stevens said, he recommended promoting Hewson to CEO.She has led the contractor's electronic systems unit since January 2010 and has been with Lockheed for 29 years.The sudden turn of events means Hewson will become the company's first female chief executive, and her ascension comes as Phebe N. Novakovic takes over as CEO and chairman at rival defense contractor General Dynamics on Jan. 1.Stevens said that although he had been phasing out his role, he and Hewson will "rework that plan to some extent."He promised Friday to take an active role in the transition throughout 2013.Kubasik's departure should create no lasting problems for Lockheed, he insisted."I don't believe the company's in crisis," he told reporters. "We've acted cleanly, clearly and decisively. ... The very good news is that we have a significant bench strength of executive talent in this company."