Please be aware that Istanbul has multiple airports and that these results are for all airports serving the city.
The best month to fly between Istanbul and Ankara is January and the most expensive month to fly is April. (Average prices, based on 220 datapoints.)
The best day to arrive at Istanbul is Friday and it would be best to avoid Monday, as prices are on average 67.11% higher than on Friday. (Average prices, based on 235 datapoints.)