 DALLAS AP - Airlines are piling up billions of dollars in additional losses as the pandemic chokes off air travel, but a recent uptick in passengers, however modest, has provided some hope. American Airlines on Thursday reported a loss of 2.4 billion and Southwest Airlines lost 1.16 billion in the third quarter, typically a very strong period of air travel that includes most of the summer vacation season. Revenue plunged at both airlines. Combined with earlier losses reported by Delta and United, the four largest U.S. airlines have lost at least 10 billion in each of the last two quarters. Its an unprecedented nosedive that has caused the once highly profitable airlines to forage for billions of dollars in government aid and private borrowing to hang on until more travelers return. The airlines, however, are offering upbeat forecasts about Thanksgiving and Christmas travel, even as many states report an increase in confirmed virus cases. Southwest feels confident enough that it will stop blocking middle seats on its planes Dec. 1. Southwest and Delta are among a handful of airlines still limiting capacity to reassure passengers who are nervous about packed planes during a pandemic. Southwest said it will drop that policy because of science-based findings from trusted medical and aviation organizations about how COVID-19 is spread. Airline groups and aircraft manufacturers, relying in part on research by the military, say that strong cabin air flow and high-efficiency filters make planes safer than other indoor settings. There is a financial angle too, as flights become more full. Southwest said it turned away 20 million in ticket sales in September and estimated it could lose 40 million in November. Delta plans to stop blocking seats in the first half of next year. American and United have long tried... 