(Adds details on process, Turkish market)
ISTANBUL, Aug 29 (Reuters) - Turkey's competition board has launched an investigation into Turkish Airlines after its rival Pegasus complained it had abused its dominant position in the market.
Low-cost airline Pegasus first filed a complaint against the national flag carrier in 2011, accusing it of using its dominance to prevent rivals from entering new markets.
The complaint was initially rejected by the competition board but Pegasus went to court and won an appeal ordering it to investigate, the regulator said in a statement on its website on Thursday.
Turkish Airlines and Pegasus are two of the world's fastest- growing airlines in terms of passenger numbers and aircraft acquisitions and competition on both domestic and international routes is intense.
The national carrier transported 39 million passengers last year and expects to reach 46 million this year, a figure it plans to double by the end of the decade.
Pegasus, which has increased its fleet from just two aircraft to more than 40 over the past two decades, carried 13.6 million passengers last year.
The regulator has to rule within two years in such cases. (Reporting by Orhan Coskun and Seda Sezer; Editing by Nick Tattersall and David Holmes)