Dec 4 (Reuters) - United Airlines Holdings Inc said on Friday it had adopted a tax benefits preservation plan to protect the company’s ability to use its large net operating loss carryforwards to reduce future federal income tax expense. The company said it had net federal operating loss carryforwards of about $8.2 billion as of the Sept. 30. (Reporting by Uday Sampath in Bengaluru; Editing by Sriraj Kalluvila)