Florence airport Amerigo Vespucci is relatively close to the city centre, approximately 4 km. If your flight lands in Florence you can take the bus from the airport to the main train station Firenze Santa Maria Novella. The service is available from 5.00 a.m. to 8.00 p.m. every 30 minutes and from 8.00 p.m. to 11.00 p.m. every 60 minutes.
The Pisa airport Galileo Galilei is a small but convenient airport. The Pisa Airport is about 1 km from Pisa Centrale railway station, from which you can reach any Italian railway network destination. To reach Pisa Centrale train station you have many options such as bus or car, but the easiest is the People Mover, an airport shuttle available every day from 6:00 AM to midnight at 5/8 minute intervals.