Istanbul airport timing

If you spent any time in Turkey before arriving at IST airport you will need to have your passport checked before exiting the country. But if you’re only passing through IST airport because of flight connections and you never left airports while in Turkey, you will not have to go through passport control ( Immigration) which is the same desk that checks visas. . Buy your air ticket to Greece online in advance ( www.Skyscanner.com ) get your boarding pass QR Code online 24 hours prior to your flight departure and you’ll be good to go. Providing your flight arrives at IST on schedule you should be fine with 2.5 hours. Turkish Airlines schedules flight transfers at IST with as little as 90 minutes and that’s even with passengers having to go through Immigration.

Thanks
My travel agent this afternoon told me I would need to exit the terminal and check in for the new flight, as I cannot check in for an international flight online without them siting my passport . Are you saying there is somewhere I can do this in the terminal without going through immigration?
We will have already spent 30 plus hours travelling (22 of them in the air) before we land in Istanbul, so printing anything before we leave is impossible

Thanks
Sharon

https://www.istairport.com/en/passenger/airport-guide/transfer-transit-passenger-services?locale=en

Until someone shows up with better info, the above seems to imply you can make the transfer without 'officially' entering Turkey.

If Athens is your destination why are you not booking a ticket to Athens ( with protected connections) rather than the unrelated succession of flights?

Thanks.
We were initially going to spending time in Turkey,, hence our flight, which was booked months ago. Plans have unfortunately needed to be changed so we are heading straight to Athens to meet our commitments

but you are not checking bags? right? cause that complicates things on two tickets..... better, if you can, to "change" your original ticket rather than buy a seperate ticket .... for a lot of reasons.

On one ticket I have made 1 hour connections in IST a couple of times, but not fun physically or emotionally.

Unfortunately the option to cancel and rebook is cost prohibitive.
The time between flights is 2 hours 40 , or there is another flight at 3 pm, but if the morning flight is doable, we would prefer to get to Athens than stay in an airport for 6 to 7 hours

If you miss your connection, you lose your ticket. So it comes down to, do you feel lucky? If you don't have checked luggage it's reasonable in 2:40, but if you have to claim and recheck .... well .. ...

I would be tempted to take tge later flight and check into the terminal hotel and take a nap. I've actually done that twice at IST on 8 hour layovers.

I would go by your travel agent’s information and plan on the long slog. Not sure when your trip through IST is ( high-season? During Ramadan 3/23-4/21?) or how many are in your travel group, or if there are any mobility issues, but IST is a gigantic airport that involves a lot of walking with few moving sidewalks. The signage at the airport is sparse during the mile or more of walking that is involved. Worldwide, it is second only to the Dubai Airport in the number of international passengers passing through its terminal annually. That means you will need extra time to exit the secure area and re-enter through security to check in for the Athens flight. Be sure you adhere to all the rules for carry-on luggage or a delay may occur.
IST’s website says to arrive at the check-in counters 2 hours prior to your international flight’s departure time. It will take some time for your flight to taxi to the gate, passengers to disembark, make your way through the terminal to exit for the check-in counters after re-entering through security. As suggested above by Mister E, you might want to take a flight to ATH three hours or more after you arrive at IST to build in a buffer in case of any unpredictable delays.