UPDATE 1-Turkish Airlines seals $5 bln Boeing 777 order
* Deal finalises order for 15 Boeing 777-300ER aircraft
* Turkish carrier has options for five more
* Deal is largest by value for Turkish Airlines
Dec 10 (Reuters) - Turkish Airlines has finalised an order worth $4.7 billion at list prices for 15 Boeing 777-300ER aircraft, marking the biggest order by value in the airline's history, the U.S. planemaker said on Monday.
The order, firming up a deal tentatively announced in October, includes options for a further five of the same type of 365-seat aircraft, Boeing said in a statement.
The deal almost doubles the number of net orders in 2012 for Boeing's most profitable plane as the U.S. company closes out a strong year dominated by sales of smaller 737s jets.
Turkish Airlines is the world's fastest-growing carrier and a key battleground for the world's dominant planemakers.
Its chief executive said earlier this year the airline was also studying the purchase of the latest design of medium-haul jets offered by Airbus and Boeing.
Shares in Turkey's national carrier rose about 1 percent. In early U.S. trading, Boeing shares were up 0.3 percent.
Boeing looks certain to win the annual order race against its European rival Airbus this year, according to latest data from the two companies.
Boeing sold record numbers of 777 aircraft in 2011 but sales of the company's premium wide-body plane have slowed in 2012 as the civil aerospace cycle slows down. As of Dec. 4, the U.S. manufacturer had sold a net total of 17 777s this year.
Boeing is weighing options for a refreshed design of the 777 to counter the future A350-1000 from Airbus.