American Airlines said Friday that the government is investigating whether companies that distribute airline flight and fare information are violating federal antitrust laws.
One of the companies confirmed that it has been contacted but said officials have made no allegations against the distribution systems, which act as middlemen between airlines and travel agents.
American said it received a civil demand for information from the Justice Department. The airline declined to release the document but said it welcomed the investigation.
"American is not the subject of the investigation," said spokesman Andrew Backover.
Sabre Holdings, one of the largest so-called global distribution systems, said it received a request for information.
"There are no allegations," said Sabre spokeswoman Nancy St. Pierre. "We believe they have contacted others as well. We are cooperating fully."
Another big distribution company, Travelport Ltd., did not immediately respond to messages for comment.
American is fighting with global distribution systems over the way information about flights and fares is shared with travel agents. American wants to deal more directly with travel agents and reduce the amount it pays to the distribution systems that charge fees when consumers search for and book flights.
Many consumers go directly to airline websites, but corporations often use travel agencies that rely on information from the distribution systems.
Last month American sued Travelport, accusing it of monopoly tactics and retaliating against the airline by burying information about its flights. Travelport's systems handled $2.7 billion in American ticket sales last year.
Travelport and Orbitz Worldwide Inc., an online travel agent partly owned by Travelport, countered that American was trying to control ticket distribution to limit consumer choice and reduce competition. American pulled its flight listings from Orbitz in December as the dispute began to heat up.
American, a unit of AMR Corp., also sued Sabre, but the two are discussing a settlement. US Airways also sued Sabre.
American settled a similar dispute with another online travel agent, Expedia Inc., and information about American flights can again be found on Expedia.