* Turkish Airlines decides to exercise option
* Purchase is part of order of up to 105 planes
ISTANBUL, Oct 30 Flag carrier Turkish Airlines (THYAO.IS) said on Friday it will exercise the option to buy three Airbus A330 planes, part of its ambitious fleet-expansion plans to gain market share in Europe.
Europe's fourth-biggest airline by passenger numbers will take delivery of the planes in 2012, according to a filing issued to the stock exchange.
Turkish Airlines announced in October 2008 that it would buy up to 105 planes from Airbus EAD.PA and Boeing (B.N), worth about $6 billion at list prices.
The planes, to be procured between 2010 and 2012, would nearly triple the state-run carrier's fleet and help it grab market share from European peers Lufthansa and Air France, analysts have said.
The order includes options for 30 planes, the Istanbul-based airline said previously.
Turkish Airlines shares fell 3.21 percent to 4.22 lira, compared with the blue-chip index's 3.52 percent decline. (Writing by Ayla Jean Yackley; Editing by David Cowell)