Get in Pisa - Airport “Galileo Galilei”
Pisa has regular trains to and from Florence (usually three per hour), to and from Lucca (usually every hour) and is also accessible by bus, and has an international airport.
Also there are trains from La Spezia and Genova.
Pisa Airport “Galileo Galilei” is the main airport of Tuscany and is served by several airlines operating hundreds of weekly flights to national and international destinations. Numerous companies offer charter flights to and from a number of European and non-European destinations. Flying to Pisa is really cheap and easy: the most recognized low-cost airlines serve Pisa. The airport is close to the city center - it takes only a few minutes to reach the center by bus, train or taxi. It is even possible to walk to the center, which takes around 20 minutes.
Do not expect the airport to be open 24/7, though. Many smaller European airports do have opening hours, so don’t expect to stay overnight or hang out until late.
You can purchase bus and train tickets from the information desk in the arrivals hall. The trains are the fastest way to get to the city. The tickets cost €1.10 and the ride takes only about five minutes. However, the trains are not very frequent. There are only two per hour. The bus has a regular service every 15 minutes and it takes about 15 minutes to get to the city. The bus runs to Piazza dei Miracoli and the central station. Since the ticket machine at the bus stop only “speaks” Italian, it’s better to get the tickets from the information desk if you don’t speak the language. Single fare is €0.95, but if you buy them from the driver on the bus, you pay double. The bus terminal is directly in front of the airport, on the right side when coming out of the terminal building. Once in the city, its main sights are easy to locate and are all within walking distance.
If you prefer a more convenient method of travel, a Taxi to the city center will cost around 6-8 Euro.
Sources: Wikipedia

