Aeroporto di Firenze-Amerigo Vespucci (Florence-Amerigo Vespucci Airport).
Once you arrive in Florence by plane, I recommend to take the bus called Volainbus which, in about 20-25 minutes, will take you to the centre of the city. The bus station in Florence is opposite the railway station. From that place, all the main sights are within a walking distance (apart from where your accommodation is). The Tourism Office is also a few meters away.
It runs every 30 minutes: