Turkey's competition regulator is to launch a fresh investigation into Turkish Airlines, based on a complaint filed by the flag carrier's rival Pegasus Airlines.
Pegasus has contended that in 2010 Turkish Airlines abused its dominant position in the market by engaging in exclusionary practices with its domestic and international flights departing Istanbul.
Sabiha Gökçen airport in Istanbul is Pegasus's main base, while Turkish Airlines is based at Ataturk.
The regulator had decided there was not enough evidence for imposing a fine on the national airline and acquitted it of the charges.
However, an Ankara administrative court recently reversed the regulator's December 2011 judgment, leading to a reassessment of the complaint.
The regulator stresses that the launch of a probe does not necessarily mean the airline will be fined.