Franco-Dutch carrier Air France-KLM (AF.FR) has agreed to jointly operate transatlantic routes, sharing revenue and costs for at least 10 years with U.S. airline Delta Airlines Inc. (DAL).

The venture represents about 25% of the industry's total transatlantic capacity and will sharpen the two airlines' ability to compete against other airline alliances, the companies said in a statement Wednesday. Based on 2008-2009 data, the annual joint venture revenue is estimated at $12 billion, the companies said.

The venture tightens Air France-KLM's links Delta, as they already work together in the SkyTeam multi-carrier alliance. It follows the merger last year of Delta and Northwest Airlines, which created the largest U.S. carrier.

The Dutch arm of Air France-KLM has had a longtime partnership with Northwest.

The new venture will run more than 200 transatlantic flights and about 50,000 seats daily, the companies said.

Air France-KLM declined to say whether the number of flights or seats available under the venture is an increase or reduction from the current combined totals of the carriers.

The partnership encompasses all flights between North America and Europe and extends outside the region to include routes between Amsterdam and India, as well as North America and Tahiti. "On these routes, strategies and economics are to be equally shared among the Air France-KLM Group and Delta," the companies said, without elaborating.

They added that the venture has no defined end date and can be canceled with three years' notice after the initial 10-year term.

"The signing of this joint venture agreement is taking place in the wider context of the liberalization of air services between the European Union and the U.S.," the companies said. It represents a broad network of routes, new destinations, multiple flight frequencies, a wider range of fares and a harmonized product in the air and on the ground, they added.

Air France-KLM declined to comment further the statement until a joint press conference with Delta at 1000 GMT.

Company Web sites: www.airfrance.com; www.delta.com.

-By A.H. Mooradian, Dow Jones Newswires; +33 1 4017 1740; art.mooradian@dowjones.com.