US Airlines Face Price-Fixing Investigation

The US Justice Department has said it is investigating some airlines over "possible unlawful co-ordination".

The civil antitrust inquiry follows a period in which domestic flight ticket prices have kept rising despite the plunge in fuel prices.

Major US carriers received a letter from the authorities on Tuesday demanding copies of their communications.

The request focused on correspondence relating to the airlines' plans for passenger-carrying capacity.

A Justice Department statement said simply: "We are investigating possible unlawful co-ordination by some airlines."

There was no mention of which airlines were covered in the inquiry, but the news sent shares of major US carriers sliding.

Two weeks ago, Democratic Senator Richard Blumenthal urged federal authorities to investigate the aviation industry.

He wrote in a letter: "Consumers are paying sky-high fares and are trapped in an uncompetitive market with a history of collusive behaviour."

According to Department of Justice data, available seat miles on US carriers remain significantly below the peak in late 2007, a year before a series of mergers began.

That consolidation left American Airlines, Delta Air Lines, Southwest Airlines and United in control of more than 80% of seats in the domestic travel market.