Nowadays, flying to Tuscany is easy and cheap. Tuscany has two international airports that are well connected with major airports of the world: Amerigo Vespucci Airport in Florence and the Galileo Galilei International Airport in Pisa.
If you are planning a journey around the north of Tuscany, (Lucca, Pisa, Florence or La Garfagnana) Pisa Airport is the best option. Flying to Florence is expensive and not worth it as it is just located 80km away from Pisa. Low cost companies, such as Ryanair and easy Jet, fly from main European cities to the Galileo Galilei International Airport. If you are flying from United Kingdom, London Stansted, Leeds, Liverpool or East Midlands are some of the airports where you will find great reasonable prices to travel to Pisa during the whole year.
If you are flying from London Stansted airport, flying to Perugia could be an alternative. You can find cheap flights with Ryanair. This city, located in the south of Tuscany, is located 100km away from Siena and it is well connected with other major cities.
However, Tuscany is not a big area. It can be traversed by train, car or bus in a matter of hours. Therefore, you could consider flying to Rome as it might be cheaper. Renting a car, getting a train or a bus can be the easiest way to travel around Tuscany.