Few days ago, Turkey started easing up on COVID regulations across the country. Now, new regulations for domestic flights are announced. 
Apparently, passengers are no longer required to undergo PCR tests for domestic flights, regardless of their vaccination status! However, international flights are a different matter. Based on where you are going, or where you are coming back from, the regulations might differ! But usually you are required to undergo a PCR test 72 hours before the flight and provide a negative result on your PCR test. So, always check with your travel agency to be sure.
Apparently, passengers are no longer required to undergo PCR tests for domestic flights, regardless of their vaccination status! However, international flights are a different matter. Based on where you are going, or where you are coming back from, the regulations might differ! But usually you are required to undergo a PCR test 72 hours before the flight and provide a negative result on your PCR test. So, always check with your travel agency to be sure.