Typical responses.
It is one thing in principle to agree to increase the number of flights between two countries, but in practice it is more difficult because only a certain number of take-off and landing slots per hour for each runway. Thus, one of the problems for airlines is the availability, timing, and cost of such slots, which can cost millions of US dollars each. The average cost of a landing slot at London Heathrow Airport, for example, was around USD 2.5 million (
https://www.iba.aero/insight/what-is...december-2019/). Istanbul Airport is already the busiest in Europe and the world's second busiest, so I expect the competition for new slots will be fierce - and their cost increasing.
The other problem is the availability and cost of all the other airport services an.airline uses, e.g., check-in counters, arrival/departure gates, and so on. The list of tariffs for Turkey's airports' services for 2022 runs to more than 60 pages (
https://www.istairport.com/tr/busine...fesi-en-v2.pdf). Of course, these tariffs are factored into ticket prices, but the landing/take-off slots must be purchased first for a scheduled airline.