First Take: Uncertainty for airlines, status quo for fliers

The Justice Department threw a curveball this morning in announcing it would try to block the American-US Airways merger that would have created the world's biggest airline.

The move comes as a surprise to many industry observers, in part because the merger had already won regulatory OKs from both the Department of Transportation and from European regulators.

But — perhaps of more significance — Justice's suit also appears to signal a shift at the agency, which approved three other big airline mergers — United and Continental, Delta and Northwest and Southwest and AirTran — all within the past five years.

Apparently the American-US Airways merger — which would have been the biggest of the bunch — was a step too far to win Justice's OK.

For now, the merger will be on hold. It could eventually win clearance pending concessions or a new merger proposal from would-be partners American and US Airways.

Despite the uncertainty for the airlines, the move will have little immediate effect on fliers. The airlines — and their frequent-flier programs — will continue to operate independently.

Even if the carriers do eventually win clearance for the deal, it now likely will come much later than the carriers' executives had expected.