The takeover by Delta, the nation's third-largest airline, of number-five Northwest creates a new mammoth airline that keeps the Delta name and, like its namesake, is headquartered in Atlanta, Georgia.
The new airline serves customers in 66 countries and more than 375 worldwide cities -- "more than any other airline" -- with a worldwide workforce of approximately 75,000 employees, Delta said.
"The airline industry faces a very difficult economic environment around the world and this merger gives Delta increased flexibility to adapt to the economic challenges ahead," said Delta chief executive Richard Anderson.
With the completion of the merger, Northwest Airlines is now a wholly owned subsidiary of Delta, it said.
The merger comes amid consolidation in the aviation sector as airlines struggle to survive amid high fuel