Originally Posted by
Intl359Widget
However since your flight is 21h later they might not allow you to go through International Transfers (Security) and even then they may not allow you into the lounge if it's for a next day flight.
No such rule (e.g. visa/entrance to Türkiye rewuired for connecting time >12h) in IST IMO. Those rules are mostly for airport capacity reasons which IST clearly does not have problems with. But why waste 21h layover in the airport? Go and see the city, experience turkish hospitality and food in the town. Also, they will not allow you to sleep in the sitting parts of the lounge