How should you plan a separate domestic flight from Istanbul, for example to Antalya, if you're already flying into Istanbul on an international ticket?

If Istanbul–Antalya fares look cheap, travelers usually book them as a separate leg: one international round trip to Istanbul, plus another domestic round trip between Istanbul and Antalya.

With this setup, don't focus only on the low Antalya fare: calculate the whole route, because you'll effectively have two separate tickets and will need to manage the connection timing yourself.

Plan hotels ahead as well: with separate tickets, you may need an overnight stay in Istanbul before or after the domestic flight, especially if the schedules don't line up well.

If your question is not about a domestic flight but about crossing between the Asian and European sides of Istanbul, the best route depends on your exact starting point: a short cross-city transfer is different from traveling across the whole city.