The attorney general of Texas and counterparts in other states joined a U.S. Department of Justice review of the proposed merger between American Airlines and US Airways.
A spokesman for Texas Attorney General Greg Abbott says that Texas and 18 other states entered the federal antitrust review. He declined further comment.
The companies announced in February that they planned to merge in a deal that would create the biggest airline in the world.
Members of Congress have raised concern that if combined, American and US Airways would control about 70 percent of the takeoff and landing slots at Reagan National Airport outside Washington, D.C.