Bucharest is served by two public airports which are fairly close to the city and very well connected via bus, taxi and other transit services. By far the most affordable option and efficient means is in bus.
From Henri Coandă International Airport: Otopeni
This is the main International Airport which is served by TAROM and other major airlines. The best option to get to town besides a taxi is Bus # 780 or 783, it stops just underneath the arrivals hall, it is a good option to get into the heart of town: Piata Victoriei, Piata Romana and Piata Universitatii. It departs every 30 minutes during the day, and then every 40 minutes at night.
One must purchase an Activ Card before boarding, it cannot be bought on the bus but from any of the kiosks around the terminal or outside it can be. One can buy credit for a single journey, for use during the whole trip or for a roundtrip ticket.
From Aurel Vlaicu International Airport: Băneasa
This airport is used mostly as the low cost hub situated 8 km north of Bucharest city centre and is accessible by RATB buses 131, 335. Many of the late arrival low cost flights come after the bus finishes service and thus a taxi must be negotiated. To take the bus, exit the terminal and walk out to the road, cross the road for buses headed South towards the city. 301 is a less frequent bus and you can catch 780 and 783 coming from Otopeni Airport towards the city.
Buses run Mon-Fri every 15 mins 0530-2340. Weekends & Holidays every 30 mins 0530-2330. It takes about 20-45 mins to the city.