The new airline, to be called Delta, will continue to be based in Atlanta, but will have executive offices in Eagan, Minn., where Northwest has its headquarters.

Delta CEO Richard Anderson will be chief executive officer of the combined company, which will retain the hubs of both Delta and Northwest, including Delta's operations at Salt Lake City International Airport, which could benefit from improved access to international destinations.

"Delta and Northwest are an excellent strategic fit, with complementary and geographically distinct route systems," Delta President Ed Bastian said in a statement.

"Together, we will have a more robust platform for profitable international growth. Combining both carriers' international land domestic strengths, with our worldwide SkyTeam partners, we are well positioned to lead the industry and deliver value to our shareholders."

The deal, an all-stock transaction valued at $17.7 billion, awaits approval by federal regulators. It would create the biggest airline in the world in terms of passenger traffic, while preserving seniority protection to employees and giving them equity in the new carrier.

"Today, we are announcing a transaction that is about addition, not subtraction, and combines ... networks that open a world of opportunities for our customers and employees," Anderson said.

The deal was completed without a prior agreement about seniority from the unionized pilots of both airlines.