Atatürk Airport
Most planes arrive at Istanbul Atatürk Airport (IATA: IST), 20 km west of the city centre. From the airport, there are various options for getting into Istanbul: you can take a taxi (about 35-40 TL to Taksim. There is no night fare in Istanbul anymore - the price would be the same at midnight or midday. About the same to Sultanahmet), the express bus service run by the local airport service called "Havataş", which departs half-hourly between 4AM-midnight and costs 10 TL to Taksim and Aksaray and Kozyatağı), the public bus (line №96T) run by İETT costing 5 TL (3.5 with İstanbulKart), which has fewer departure times now, due to Havatas, which is also a municipality engaged bus service.
Then, there is the metro (6:00 - midnight) (signposted "light rail" in the airport, when you get outside the baggage claim its about a 10 minute walk in the airport to the metro line. Just follow the signs), which will take you directly to the Otogar (bus station) or to numerous stops within Istanbul (Aksaray in the city centre is the last stop, transfer stations for tram heading for deeper into old city is available at Zeytinburnu and Aksaray). It costs 3 TL, by token (+an extra 3 TL when boarding the tram) and getting to Aksaray takes around 45 minutes. It is possible to be at your bus departing from Otogar within less than one hour after landing by taking the metro.
When entering the metro station, you need to buy a jeton (token) for 3 lira. Just hand the cashier 3 lira and he'll give you a token, or use the automatic dispenser (Jetonmatik), which accepts banknotes (5 TL, 10 TL) as well as coins. Use 'select' to choose the number of jetons and then push 'ok'. They don't accept credit card or foreign currency here. This will get you on the red metro line (towards Aksaray). From this line, if you are going to Sultanahmet, you can transfer at Zeytinburnu and buy another jeton (3 lira) - see the section on "Istanbulkart" if further travel within Istanbul's metro system will be undertaken. Note that the jeton token here is different than the first one. From Zeytinburnu, take the blue tram line T1, towards Kabataş which passes by: Sultanahmet, Eminönu and Tophane. The trip from the airport to Sultanahmet takes about 45 min.
Other Notes: Note that people are working on commission at the airport trying to make you use special shuttle buses for very high fees (30+ TL), so for people who wish to travel more economically the Metro/tram-combination is easy and fairly quick, and offers very good value. Travel by metro/tram cost 1 token per trip which is equal to 3 TL. No matter how long you travel, it cost 1 token per trip.
Visa: Depending on nationality, foreigners arriving in Istanbul may need to purchase tourist visas (USA and some EU citizens, depending on exact nationality, do). This must be done upon arrival before queuing for passport control. The windows for purchasing the visa are located immediately to the left of the main passport control booths. You must pay in cash US dollars, Euros, or British pounds. Turkish lira is NOT taken or you can pay by Mastercard/Visa at the visa desk.
Note that food and drinks at the airport may cost up to five times more than in the city proper, like in other international airports. If you are traveling on budget and plan to spend some time at the airport, it may be wise to bring your own meals from town instead of buying them there. If you come from the Metro, there is a supermarket in the tunnel leading to the elevators / stairs to the airport proper where you can do some last-minute shopping.
Sabiha Gökçen Airport
Istanbul also has a second airport, Sabiha Gökçen International Airport (IATA: SAW), located in the Anatolian side of the city.
The cheapest way to arrive from Sabiha Gökçen in the European side of Istanbul is by bus (E10 line, from Sabiha Gökçen to Kadiköy) + ferry(from Kadiköy to many ferry stations, including some in the Sultanahmet area). It costs no more than 7TL for the bus ride and then you pay only 2TL for the ferry ride (which is linked to the public transport system, meaning you can also use akbil or electronic transport prepaid cards to pay for the ferry). That's less than €4 in total. Every other option priced at €10 and above ( 23 lira and above-by Feb 2013 rates) makes sense ONLY if you can't use this. And BEWARE of the company running the "HOTEL INFORMATION" office in the Sabiha Gökçen airport, see below.
A Havatas bus connects this airport with Taksim in the city centre for 12 TL (March 2013) and takes about an hour (closer to two or more in heavy traffic). There is also a Havatas service to Kozyatağı, a transportation hub of Asian Side, which costs 10 TL. If you arrive in the middle of the night, you can move to the departure hall after passing customs and rest on very comfortable seats — you will even find coin-operated Japanese massage chairs. Then, at 05:00 the first Havatas bus will take you to town. The Havatas bus schedule is sometimes linked to the arrival/departure times of planes.
A cheaper option is to take public bus line #E9 to Kaynarca (get off at Tersane Lojmanlari) in (30 min, 2 TL); see timetables. From Kaynarca, you can take a suburban train (Banliyö Treni) to Haydarpasa (50 min, 2 TL), from where you can take a ferry to Karaköy (2 TL). Total travel time is approx. 1 h 40 min and the cost 6 TL.
Various private operators offer internet bookable shared minibuses to central locations — a good choice when arriving late. A typical price being EUR 90 for 4 people to a hotel in Laleli. A taxi to Sabiha Gökçen airport from Taksim, which lies around 50 km from the airport, takes ~35 minutes at 3:30am with no traffic. The meter will show ~65 lira, plus there is ~6 lira in tolls. Note the security screening is before the check-in counters, so add some extra time to make the cutoff times (45 minutes for international, 30 for domestic).
Beware of the company running the "Hotel Information" office in the Sabiha Gökçen airport which offers "shuttle-to-hotel" services from €15 (they pretend to make a discount based on your group size, you can get it as low as €12.5 for 4 people) because their drivers are totally uninformed about any hotel address and they may get lost/the trip may take 2-3 times more than normal because of their lack of knowledge with hotel addresses.
When arriving at Sabiha Gökçen airport, there are people offering shuttle services to the European side of the city, most costing €10, which is much cheaper than booking a taxi with your hotel/hostel (about €50-60). It is the best option after the Havatas airport buses. For the return journey, officers are quite zealous with luggage checks and they systematically remove the cap from bottled water once at the gate. It is recommended not to buy water before the flight although you can take the open bottle on board. Another surprising feature of Sabiha Gökçen airport is the luggage check at the main entrance, but fortunately you are allowed to take drinks in the airport at this point.
