At Raleigh-Durham International Airport, the world's largest airline will still trail rivals Delta Air Lines, American Airlines and Southwest Airlines.

United and Continental announced this morning that they're joining forces to form United Continental Holdings. If the deal wins shareholder and antitrust approvals later this year, the company would pass Delta as the world's largest carrier.

But at RDU, the combined United Continental would still offer fewer flights than Delta, American or Southwest. From RDU, United offers direct flights to Washington Dulles and Chicago O'Hare, while Continental has nonstops to Houston, Cleveland and Newark.

In 2009, Continental handled 5.87 percent of the flights at RDU, while United handled 4 percent.

Delta merged with Northwest Airlines to take the top spot at RDU last year, with 24.12 percent of flights. American and American Eagle followed with 22.88 percent. Southwest was close behind with 21.25 percent.

It's too soon to tell how the United-Continental union will effect RDU, said airport spokesman Andrew Sawyer.

The carriers are merging with the goal of boosting revenue, especially from international and corporate travel. Consumer advocates have warned that reduced competition in the airline industry could hurt consumers.