US Airways and Tempe-based American Airlines are extending their merger deadline by at least a month to wait for the outcome of an antitrust lawsuit filed by the federal government.

That trial is scheduled to begin Nov. 25. The airlines' original agreement allowed either side to call off the merger after Dec. 17, but there might not be a verdict in the trial by then. The new agreement extends the merger deadline to Jan. 18 or later, depending on when the court rules.