Many visitors to Istanbul, especially those using budget airlines, will arrive at Sabiha Gökçen, Istanbul's new airport on the Asian side of the Bosphorus.  The airport is located about 30km south east of the ferry terminal at kadikoy and is used by both international and domestic flights.  

There are a number of ways to travel from the airport to the centre of Istanbul.

You can use a private car service, taxi, city bus or the Havatas airport buses..  The journey from the airport can take as little as 40 minutes under the best conditions (06:00 am on a weekend morning, for example), but at other times you must allow 60 to 90 minutes, and perhaps even more. 

The Havatas buses depart Sabiha Gökçen for the Kadikoy ferry terminal every 30 minutes on the hour and half hour (for example, at 04:00, 04:30, 05:00 am, etc.) The first bus departs at 04:00 am, the last bus at 01:00 am. (Thus, no buses between 01:30 and 03:30 am).  The one-way fare is TL13, and the buses accept the Istanbulkart..   This is probably the best, and often the quickest way to get to the city centre, and has the added advantage of a cheap Bosphorus cruise.  You can catch the ferry from Kadikoy to Eminonu for Sultanahmet, or Karakoy for Galata and Beyoglu.  Other Havataş buses go to Taksim Square on the European shore every 30 minutes on the hour and half hour from 03:30 am until 01:00 am. The journey can take as little as 90 minutes, or much longer, depending on traffic. The one-way fare is TL18.  Click here for the Havatas bus schedules.

You can also take the municipal city bus leaving Sabiha Gokcen at frequent intervals for Kadikoy and Taksim. Bus E-10 from Sabiha Gokcen to Kadikoy, or bus E-3 to 4.Levent Metro station where you can take the metro directly to Taksim.   These buses are much cheaper but make frequent stops and are slower than the Havatas buses.  They also do not have room for heavy baggage. Click here for the E 3 and click here for E10 timetables.