Thu September 4, 2003 11:15 AM ET WASHINGTON (Reuters) - Underfunded pension liabilities at troubled U.S. companies doubled this fiscal year, and could exceed $80 billion with airlines accounting for nearly a third of the deficit, the government said on Thursday. The Pension Benefit Guaranty Corp. also told Congress its deficit has grown to $5.7 billion as of July 31. The deficit for the entire fiscal year ending Sept. 30 last year was $3.6 billion. This gives the U.S. agency less money to bail out any troubled company retirement plans. Airlines, including bankrupt United Airlines Corp. UALAQ.OB , have an...