Air France-KLM Group and Delta Air Lines Inc. are forming a joint venture that will allow them to share profits and up to an estimated $8 billion in annual revenue on trans-Atlantic routes.

The move announced Wednesday follows the new Open Skies agreement on airline service between the United States and Europe.

The venture, to launch in April, will generate an estimated $1.5 billion a year in revenue in its first phase, and $8 billion a year when fully operational, the companies said in announcing the deal at Charles de Gaulle airport in Paris.

Such a deal will be a major challenge to competitors such as British Airways, UAL Corp.'s United and AMR Corp.'s American as airlines jockey to benefit from the Open Skies deal, and some analysts said it could spur more trans-Atlantic combinations.

The venture will first apply to all nonstop flights between Air France's French hubs and Delta's Atlanta, New York-JFK, Cincinnati and Salt Lake City hubs, representing 19 flights and more than 4,500 seats per day.

Starting in 2010, numerous flights to all destinations between Europe, the Mediterranean and North America will be part of the joint venture, they added, as well as flights between Los Angeles and Tahiti.

"The partnership will be neutral for air fares, but where consumers will benefit tremendously is in more nonstop options," said Minneapolis-based travel analyst Terry Trippler.

Delta, the third biggest U.S. carrier, will benefit from three of Air France's landing slots at London's congested Heathrow airport. These routes will include a new Heathrow to Los Angeles route operated by Air France, two Heathrow-JFK flights operated by Delta and a Heathrow-Atlanta flight operated by Delta.

"You have got to have Heathrow to be competitive ... and this gives Delta the plum over there," Trippler said.

In addition, Delta will operate three new nonstop trans-Atlantic routes: Paris-Orly to JFK, Lyon-JFK and Paris-Charles de Gaulle to Salt Lake City.

Delta Chief Executive Richard Anderson said revenue estimates were preliminary but that the company was optimistic because it was able "to take its significant network assets and the significant distribution that Air France enjoys as one of the greatest airline brands in the world and couple it with a massive distribution system, a massive frequent flyer program and an extended network of Delta."

"You're actually connecting two global networks to create the world's largest global network," Andersen said.

Jean-Cyril Spinetta, chairman and CEO of the Air France-KLM Group, said, "We are hoping for several tens of millions of additional profitability" from the venture.

Air France and KLM combined three years ago, but are still being operated separately so as to retain landing slot privileges, notably at Heathrow where availability is extremely tight.

British Airways PLC has twice unsuccessfully attempted to combine with American Airlines on trans-Atlantic routes.

Collins Stewart analysts said the deal is likely to be a catalyst for wider combinations, including BA and American and Germany's Deutsche Lufthansa AG, United Airlines of the U.S. and Britain-based BMI.

Delta's venture with Air France-KLM is not yet on the same level as the Northwest Airlines Corp.-KLM partnership that has been "nothing but successful," but Trippler said he expects it to head in that direction, which would enable Delta to reap even greater benefits.

Air France-KLM shares rose 1.2 percent to 26.89 euros ($38.14) in Paris. Shares of Delta added 33 cents to $20.41 in afternoon trading on the New York Stock Exchange.

Spinetta also said Air France-KLM expects to start discussions with Alitalia SpA in the coming weeks. The airline is one of the six investors that the financially ailing Italian carrier has identified as possible buyers.