The U.S. Supreme Court on Monday declined to consider a pair of antitrust lawsuits against music labels and airlines.

In the music case, a group of digital-music purchasers alleged that major record labels conspired to fix prices on Internet-music downloads. A federal appeals court in New York reinstated the lawsuit last year, deciding the plaintiffs stated enough of a factual claim to be allowed to proceed against the music industry.

The high court, without comment, refused to consider the industry's bid to overturn that ruling.

In the airline case, a group of travel agents alleged that major air carriers conspired to reduce and then eliminate the base commission rates paid to agents. But that case wasn't allowed to go forward.

A Cincinnati-based federal appeals court, in a divided ruling, said the travel agents didn't allege facts that plausibly suggested the airlines engaged in an illegal antitrust conspiracy. The court said the airlines' actions were more likely explained by lawful, free-market behavior.

The Supreme Court, again without comment, refused to consider the travel agents' challenge.

In both cases, the losing parties argued that lower courts misinterpreted a key 2007 Supreme Court ruling that set new standards for plaintiffs to move forward in court with antitrust claims.

The defendant companies in the music case include EMI Music North America, Sony Corp. (SNE, 6758.TO) and its Sony Music Entertainment unit, Vivendi SA's (VIV.FR, VIVDY, VIVEF) Universal Music Group and Warner Music Group Corp. (WMG).

The case, which consolidated a variety of state and federal lawsuits first filed in 2005 and in 2006, alleged the major record labels in the U.S. conspired to inflate and maintain the price of digital music, in part by fixing a high price and restraining the availability of Internet downloads.

The price-fixing allegedly occurred when record labels controlling more than 80% of the market created two joint ventures to distribute music over the Internet and through their business dealings with third-party licensees.

The defendants in the airline case included American Airlines, United Air Lines and Continental Airlines.

The travel agents, who filed the lawsuit in 2003, alleged the airlines began a conspiracy to cut commissions in 1995, which eventually led major U.S. airlines to eliminate the commissions entirely.

The cases are Sony Music Entertainment v. Starr, 10-263, and Tam Travel v. American Airlines, 09-1138.

-By Brent Kendall, Dow Jones Newswires; 202-862-9222; brent.kendall@dowjones.com