Tuscany has two international airports, the Galileo Galilei International Airport in Pisa and Amerigo Vespucci Airport, also known as Peretola, in Florence. Located only 80 km apart, the Pisa airport is the larger of the two airports.
Both airports handle flights to major European cities. Pisa handles the bulk of European scheduled flights so it might be easier to find flights into Pisa if you're flying from Europe. If you're flying from further abroad, most airlines connect to a major hub city in Europe and, from there, you can choose to fly to Pisa or to Florence. I recommend flying into Florence if you're planning to use Florence as your base, as it will just be more convenient at the end of a long flight to not take any trains or buses.
Direct flights from North America to Italy are generally more expensive than stopover routes somewhere else in Europe. More affordable fares can be had if one flies non-stop to a major European city such as London or Paris and then takes a Ryan Air (low-fare European airline) flight direct to Pisa. You'll have to change airports in London and Paris, though, as Ryan Air generally uses secondary airports. This might actually make it more convenient at that point to fly into Florence rather than Pisa. Depends on your plans and base you'll be using during your travels in Tuscany.
The Pisa Airport - Galileo Galilei
These are some of the major airlines flying in and out of Pisa:
For information about arrivals and departures or airport services, consult the Information Desk in the Arrivals Area of the terminal. The desk is open every day from 7:00 AM to 11:00 PM. Make note that there is no tourism info point at the airport in Pisa.
Daily Left Luggage/Luggage Storage
If you have luggage and want to visit Pisa for the day, you can take advantage of checking your bags at the airport. The Information Desk (same as above) offers a Left Luggage service, every day including Sundays and holidays. You may check baggage every day from 9:00 AM to 7:00 PM; pick-up times are from 8:00 AM to 8:00 PM. The daily rate for each bag is €7.00. At the left luggage counter you will be asked to allow x-ray scanning of each bag, just as though it were hand or hold baggage to be going on a plane.
If you're leaving Pisa by train afterward, consider NOT leaving luggage at the airport but at the Pisa Centrale train station. The luggage deposit there is run by Profer Cooperativa, costs €5 per bag and is open every day of the week from 7am to 9pm. That way you don't have to go back to the airport to pick up your luggage. While there, you might also be interested in renting a bike: €10 per day or less if you want it for a few hours.
Moving from/to the Pisa airport
By car: The Pisa airport has direct access to both the Firenze-Pisa-Livorno dual carriageway (Pisa Centro - Aeroporto exit), to the Genova-Rosignano A12 motorway (Pisa Centro exit), to the Firenze-Pisa A11 (through the Pisa Nord linking stretch with the A12) and to road SS1 "Aurelia". The terminal is also directly connected to the Pisa Central Station by the People Mover shuttle (every5-8 minutes from 6am to midnight) and from there you can take trains to other cities, including Florence and Lucca. The train shuttle terminal is located just outside the passenger terminal.
You can also reach the center of Pisa with bus or taxi service.
All major car rental companies are present at the airport, if you're looking to hire a car right away and drive to your destination in Tuscany. You can search for car rental offers here.
By train: If you land in Pisa and need to get to Florence, you can then easily catch the new PisaMover shuttle from the airport to Pisa Centrale and, from there, take a train to Florence.
By bus: There are also a few bus companies offering service to Florence right at the airport. For both, you can buy tickets when you arrive. Either will have you in Florence in about an hour.
From the Florence airport
The Florence airport also has direct access to the Firenze-Pisa A11 motorway as well as to the A1 "Autostrada del Sole". The airport is located on the north western edge of Florence; taxis and a bus shuttle connect the airport to Florence's historical center. You can read more about the Florence airport and connections to downtown in this article.
The Bologna, Milan and Rome airports are also larger airports you can fly into. You can rent car or take the train to Florence. Train or bus shuttles from all of these airports to to the the main rail line in each city makes it easy to reach Florence.