AMR Corporation, the former parent of American Airlines, and US Airways Group announced they had completed the deal after AMR emerged from bankruptcy protection.
The new American Airlines Group is a goliath, providing nearly 6,700 daily flights to more than 330 destinations in more than 50 countries.
"Our people, our customers and the communities we serve around the world have been anticipating the arrival of the new American," said Doug Parker, chief executive of American Airlines and the former chairman and CEO of US Airways.
"We are taking the best of both US Airways and American Airlines to create a formidable competitor, better positioned to deliver for all of our stakeholders. We look forward to integrating our companies quickly and efficiently so the significant benefits of the merger can be realized."
American Airlines began trading today at USD 23.95 on the Nasdaq exchange under the ticker symbol AAL. In the first half hour of trade the stock climbed to USD 24.40.
The plan to create a third giant carrier to compete with US rivals United and Delta cleared a major hurdle in November after the Justice Department announced a settlement to resolve antitrust complaints seeking to block the merger.
Under the agreement, AMR and US Airways agreed to give up slots and other rights at seven key airports.