AMR plans to buy 460 Boeing and Airbus models in what it calls "the largest aircraft order in aviation history".
The parent of American Airlines will buy 200 narrowbody Boeing 737s and 260 Airbus EADS A320s between 2013 and 2013, and will also have options for another 100 Boeings and 365 options and purchase rights for additional Airbus planes.
"Today's announcement paves the way for us to achieve important milestones in our company's future, giving us the ability to replace our narrowbody fleet and finance it responsibly," AMR chief executive Gerard Arpey said.
The third-largest U.S. airline said it will receive about $13 billion in financing provided by the manufacturers through lease transactions, and will have the option to convert the new deliveries into variants within the 737 family, including the 737-700, 737-800 and 737-900ER.
American Airlines also intends to order 100 of Boeing's anticipated new version of the 737NG, powered by CFM International's LEAP-X engine.
The airline last ordered Airbus planes in the late 1980s and declared in 1996 that Boeing would be its exclusive airplane provider through 2018, so the Airbus order is seen as a major coup.
It follows tense negotiations where Boeing agreed to match Airbus and update its best-selling 737 medium-haul jet with new engines to offer fuel savings, marking a retreat from ambitious plans for a full redesign.
The market for narrowbody jet sales is estimated at $2 trillion over 20 years and is split between Boeing and Airbus, whose A320 has made substantial U.S. inroads.
The European company said last year it would put a more fuel-efficient engine in its A320 family and call it "A320neo", which is scheduled to enter service in late 2015.