Updated

House and Senate leaders remain at odds over labor provisions in a long-stalled FAA reauthorization bill, increasing the likelihood of another short-term legislative extension early next year to keep the agency functioning, according to government and industry officials.

Partisan disputes over changes in union-organizing rules affecting airlines -- combined with a holiday-shortened congressional calendar and distractions over the high-profile bill to extend the payroll-tax break -- have dimmed prospects for passage of a multiyear Federal Aviation Administration measure next month, these officials said.

Without such action, many FAA funding and policy decisions would remain in limbo, hampering work on new pilot-training rules, next-generation air traffic control systems and proposals for stricter controls on cargo shipments of lithium batteries.

Various congressional disputes have kept the FAA operating under a series of short-term measures since 2007. A stalemate over funding lead to a brief shutdown of some agency functions over the summer. The 22nd interim extension is set to expire Jan. 31.

The biggest remaining obstacle stems from a 2010 rule change by the National Mediation Board, which potentially makes it easier for airline workers to unionize.

The House version of the FAA reauthorization bill seeks to reverse the board's new rule, while the Senate backs the Obama administration and supports the change. The months-long impasse has been so polarizing that it has essentially been kicked upstairs for direct negotiations between House Speaker John Boehner (R-Ohio) and Senate Majority Leader Harry Reid (D-Nev.), according to people familiar with the details.

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