The U.S. Justice Department wanted the trial to start in March, saying it needs more time to prepare for the complex case. The airlines say a long delay would threaten their merger.
U.S. District Judge Colleen Kollar-Kotelly said in court Friday that March was "too far off."
The companies were close to completing a merger to create the world's biggest airline, but the Justice Department and six states sued this month to block the deal. They say it would reduce competition and lead to higher prices for travelers.