Time needed to fly an international flight on Turkish out of Istanbul Atatu

1.5 hr before international flight is risky to me. i don't think the airport is very big but it's pretty busy. the turkish flight i flew with was on time to germany.

I assume these are not connecting flights. In which you better take the early flight. An hour and a half is not enough time especially if the incoming flight is delayed. While three hours is a standard recommendation, you might slice that to two. But the bigger issue is that the check in counter often closes 45 minutes prior to departure so that means you really have only 45 mins margin. So it is the earlier flight.

I like tight connections. I'm in and out of Ataturk quite a bit. My daughter-in-law likes them as tight as I do and goes through Ataturk more often than I. Both of us would croak if we had less than two ours.

I agree that I wouldn't wait to 1 1/2 hours before. I would do the 6 hours before. I remember upon leaving Ataturk they have a security set up the second you walk thought the front door. Then you get into the line at the ticket office downstairs (not at the gate) and then when you have checked in, you then go toward your gate they have the more thorough security. Add to this the passport control line, you may have a little bit of a wait (or maybe not-of course it depends on how many flights are leaving around the same time. I realize you may do passport in Izmir that morning, but I guess I wouldn't risk it. I would skip the bus from Izmir to Ataturk as well. Have fun! Turkey was great !

Have you looked at other airlines? I know that Atlas Jet flies this route, because we took them (albeit in the opposite direction) and had a very pleasant experience. Turkish Air itself also flies this route. There is frequent service on this route, so you don't have to choose between a 6 hour and 1 and half hour layover. To find domestic flights in Turkey, use http://bulucak.com/Default.aspx. They seem to have disabled the English option since I used it, so you have to use a translator to make sure you have the correct month. But, it's like Kayak; you book directly through the airline's website, and these have an English option. Booking in advance saves money; the ticket prices, while not exorbitant, do go up closer to the flight, and some flights do sell out. Since you know the day and time you want, there's no advantage to waiting.

International airlines are growing increasingly strict about loading their planes. The published time of departure is now a very loose guide to when you must check in. Many lines close the cabin door at least 20 minutes before departure meaning the gate is closed too and you can't check in. On a recent intercontinental trip I saw one airline promising to close a full hour in advance. Here is what the Turkish Airlines site says: "Check-in will be closed a minimum of 60 minutes prior to the scheduled departure time of international flights and a minimum of 45 minutes prior to the scheduled departure time of domestic flights."
By the way, Turkish is in a heavy expansion mode, opening new routes, setting competitive prices and hiring some of the world's greatest sports stars to advertise their services. None of that eagerness means a late-comer can gamble on a flexible gate agent breaking the loading policy.