(Corrects Aug 22 story, para 8, to show SWISS 777s not yet in fleet)
Aug 22 (Reuters) - Deutsche Lufthansa AG's board of directors and supervisory board are expected to approve in mid-September an order for about 50 wide-body jets worth more than $10 billion at list prices, according to two people familiar with the matter.
The German airline previously said it expected to place such an order in the second half of 2013.
Lufthansa is evaluating Boeing Co's 787 Dreamliner, Boeing's still-to-be-launched 777X, and Airbus's A350, which made its maiden flight in June.
Final approval of the order is expected at Lufthansa's Sept. 18 supervisory board meeting, after the airline's executive board makes a preliminary decision, the sources said.
Since most delivery slots for the new planes are booked years in advance, Lufthansa is expected to buy the latest versions of the planes, such as the recently launched 787-10, the 777X-9 and the A350-1000, one of the sources said.
The order could be a mix of Boeing and Airbus aircraft, or Lufthansa could choose to buy only one aircraft type or order entirely from one plane maker, the sources said.
The new wide-body planes would replace 22 Boeing 747-400s and more than 20 Airbus A340s currently in Lufthansa's fleet.
Lufthansa's fleet has no 777 passenger planes. Its cargo operation has five 777 freighters on order, with the first delivery due in October. Lufthansa's Austrian subsidiary already flies 777 passenger planes and its SWISS unit has six on order.
The new wide-body planes likely would be delivered starting in 2018 or 2019, so it is not yet known how many would be for replacement of existing aircraft and how many would be for growth, said one of the sources.
Lufthansa is considering the 787 Dreamliner even though the new high-tech jet has suffered a string of problems, including overheating batteries that prompted regulators to ground the craft earlier this year.
In August, Lufthansa Chief Financial Officer Simone Menne said the airline was not worried about problems with the Dreamliner because "a lot of aircraft have teething problems in the beginning, like the 747-400, and now it's flying absolutely reliable for years and years and years."
Reporting by Alwyn Scott in New York and Marilyn Gerlach in Frankfurt; Editing by John Wallace