My wife and I are considering a flight home to the States with checked luggage which departs Istanbul IST airport at 9:40 AM on a Sunday. What time do we need to arrive at IST to safely make this flight?
I would arrive three hours ahead of your flight to allow for security (there's extra - some checks even just to get in to the airport), bag check, security, passport control, and likely a long walk to your gate. You should allow a minimum of 45 minutes to get to airport from the historic area of Istanbul, so I'd have a taxi or shuttle pick up no later than 5:30 a.m. [edited to change pick up time....it was early when I posted lol]
This question is asked frequently no matter the airport, almost every airline advises you arrive at an airport 3 hours before departure for an international flight. So you should be at your airport by 6:40 am for a 9:40 am departure.
I would absolutely arrive at least 3 hours early. Probably more like 3.5 or 4 if you are checking bags. We just flew home from Istanbul to the US earlier this week. There was security just to enter the airport, long lines at the check-in counters, and security again to get to the gate areas. There was even further security (although you'll already be where you need to be by then) at the gate just to take a seat to wait. The lady opened every single zipper on my luggage. Do not wait to go to your gate. Get there early so you can get through that last security check with time to spare. IST is not an airport where I would arrive on time. I would arrive earlier than on time.