The combined carrier would have a fleet of nearly 800 aircraft.

The stockholders of Delta Air Lines Inc. and Northwest Airlines Corp. in separate meetings Thursday voted overwhelmingly in favor of combining the two carriers to create the world’s largest airline by passenger traffic.

With their backing, the last hurdle the deal faces is a review by the U.S. Department of Justice as to whether it violates antitrust law.

“This is another milestone toward completing a merger that brings together two unique airlines with complementary strengths that will offer unmatched global service," Delta CEO Richard Anderson said in a statement.

Delta expects the department to issue a decision as early as November and hopes to close the deal by the end of the year, Mr. Anderson has said.

Delta held a special shareholder meeting at the Georgia International Convention Center in College Park, where 99 percent of its stock was voted in approval of the decision to issue Northwest shareholders 1.25 shares of Delta stock for every outstanding Northwest share, Delta said.

Northwest’s shareholders voted at the company's annual meeting earlier in the day in New York, where more than 98 percent of votes cast favored the merger.

The all-stock transaction is valued at about $2.6 billion.  The combined airline would be based in Atlanta and keep the Delta name.

Ninety-two percent of Delta stockholders also approved an amendment to Delta’s employee compensation program that would allow the airline to distribute 15 percent of the new company’s shares to employees at closing.

The Federal Aviation Administration last week approved the two carriers’ plan to achieve a Single Operating Certificate over the next 15 to 18 months, and the European Commission, the governing body of the EU, gave its full support for the consolidation in August.

Combining with Northwest will create new opportunities for Delta, which has been hedging its future on international routes that company officials say are more profitable than shorter, domestic flights.

The two carriers have complementary route maps.  While Delta’s main strengths are in the Americas and the Caribbean, Northwest has an extensive network in Asia, a region Delta has targeted. 

Delta launched a nonstop flight to Shanghai, China, in March and has a nonstop route to Seoul, South Korea, that was launched in 2006. 

Northwest has a hub in Tokyo and flies to the Chinese cities of Beijing, Guangzhou, Hong Kong and Shanghai.