To be honest you are talking about a Friday evening at Istanbul, the traffic will be awful and very uncertain. You never know with Istanbul's traffic on a Friday night, even on any night of the week. It might take you 30 minutes to get back to the airport or it might take you 3 hours.. Trust me I am not exaggerating.. Also if you land at 3.45 by the time you leave the airport through customs and everything, the places you would want to see will be closed to visit. But if you really really want to get out of the airport and see some stuff that is close to the airport for sure. You need to be at the airport the latest latest 8 PM for your flight, because Ataturk airport is a huge airport with a lot of flight traffic.. and international departures are generally hectic. I don't want to sound pessimistic and make you not leave the airport but when it comes to traveling internationally from Ataturk airport I am always super cautious.. Traffic and Istanbul are two words that do not go well together sadly
