American Airlines and US Airways(LCC) are expected to sign the merger documents before markets open on Monday.
The new company will be called American Airlines and trade on the Nasdaq under the symbol AAL.
Passengers likely will not see effects of the merger immediately. They will continue to book flights under the American Airlines and US Airways brands. Ticketing and frequent flier programs are expected to be combined -- at the earliest -- in 2014.
To secure the deal, the Justice Department required the airlines to give up some access at two major airports. The Justice Department said this would give opportunities to low-fare airlines.
Both Southwest(LUV) and JetBlue(JBLU) are expected to expand flights at New York's LaGuardia and Washington, D.C.'s Reagan National airports. Southwest has already said it plans to add six round-trip flights between LaGuardia and yet-to-be-announced airports.
A 2012 study by PricewaterhouseCoopers found airfares "have not increased significantly" since 2004. Since then, a series of mergers produced the landscape of major carriers that exists today.