The move is part of a fleet renewal plan that Europe's largest airline said could rise to 110 next-generation aircraft including 60 options also placed with the planemakers.
The decision to split the order was widely expected since the French and Dutch flag carriers, which merged in 2004, operate both types of aircraft.
Boeing is delivering its first 787 Dreamliner to Japanese airline ANA next week after three years of delays. Airbus plans to deliver its first A350 mid-decade after earlier delays in design.
Air France-KLM said it aimed to operate 73 of the 250-300 seat aircraft through 2024, including 43 Airbus A350-900 and 30 Boeing 787-9 models.
The first Boeing 787-9 will enter into service with KLM in 2016 and the first Airbus A350-900 with Air France in 2018.
"Later, both airlines will operate both types of aircraft," the carrier said in a statement. The airlines merged in 2004 but maintain separate networks.
Final details of the order are still being negotiated.
The firm part of the order for 50 aircraft is worth $6.7 billion to Airbus and $5.5 billion to Boeing, according to list prices. Airlines usually obtain significant discounts.
Air France-KLM had been weighing the order for at least a year and indicated in June it would follow United Airlines in splitting the order between Airbus and Boeing.
The plane order guarantees business for Britain's Rolls-Royce to provide power for the A350-900, for which it makes the only engines currently on offer.
But industry sources say rival General Electric is front-runner to power the Boeing 787s, for which it competes with Rolls-Royce. Air France traditionally buys long-range engines from the U.S. company.
Shares in Air France-KLM were up 1.4 percent at 6.15 euros in early trade. Shares in Airbus parent EADS were 0.8 percent firmer at 22.44 euros.
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Source : http://www.reuters.com/article/2011/09/16/airfrance-klm-aircraft-idUSL5E7KG0CG20110916