Chhatrapati Shivaji International Airport is the second busiest airport in the country in terms of total and international passenger traffic after Delhi, and was the 14th busiest airport in Asia and 29th busiest airport in the world by passenger traffic in calendar year 2016 handling over 44.68 million passengers. The airport is the second busiest in the country in terms of cargo traffic also. It won the 2015 ASQ Best Airport Award in the 25-40 million passengers per annum category by Airports Council International. It has also won the "Best Airport in India and Central Asia" award at the Skytrax 2016 World Airport Awards.
The airport consists mainly of two terminals (for Domestic & International purposes) - both terminals use the same airspace but are 4km apart. There is a free shuttle bus connecting them but be prepared for long delays through security. Going from Domestic to International you are taken outside the airport and you will re-enter through International Departures.
Terminal 1 is used for domestic flights. This was the original Santacruz building that was once used for international and domestic operations and was previously known as 1B. It was refurbished several times over the decades, the most recent being during the 2000s. It is used by SpiceJet, GoAir and IndiGo.
The new T2 terminal building operates Multiple Aircraft Ramp System (MARS) stands and swing gates, so that a single stand can accommodate either one wide body aircraft or two narrow body aircraft, in either domestic or international configuration. The new terminal is connected by the six-lane Sahar Elevated Access Road to the Western Express Highway.
Mumbai Airport - Wikipedia
The airport is 28 km from downtown. Take a prepaid coupon taxi to minimize hassle. Never pay more than Rs 450-600 for a prepaid taxi. This amount should get you all the way to the southernmost point of Colaba, the main tourist district.