lawyers are likely to include people like Ryan, who successfully argued the Apple trial last month.
The efforts are designed to help the Antitrust Division avoid any repeat of a major loss in 2004, when it tried but failed to block Oracle Corp's takeover of PeopleSoft.
AMR and US Airways will need to think hard if they are committed to following through on pledges to fight, said Evan Stewart, an antitrust lawyer in New York.
"Time is not the friend of these merging companies. Litigation as a playing-out-the-clock process is something that helps the government," he said.