air travel in Europe

Look at Vueling and Easyjet. Always read and be aware of VERY strict luggage rules. I always prepurchase the check in luggage fee even if not sure i will need it as it is much more expensive if you are told bag is oversize or weight at airport( and as I said they are strict) . I do not pay extra for preboarding or insurance etc. I am paying a total of 98 euros for a flight for two of us Barcelona to Paris,, a good deal . Purchasing sooner rather then later gets best prices, they just go up. Do not choose a airline( I am thinking Ryannair ) that flys into Paris Beauvais airport as that one is almost 100 kms from city and public transport into city is long and less frequent.
Orly and Charles de Gaulle are much much better choices.

Alba, I've always had good service with EasyJet but unfortunately I don't believe they operate from Florence. You'd need to take the train to either Pisa or Bologna. The flight from Pisa goes to Paris / ORY which is still a good choice, while the flight from Bologna is to Paris / CDG. Flight time is about 1H:40M. Vueling does operate flights from Florence to Paris / ORY, however there's a layover in Barcelona in most cases, so overall travel time is going to be longer. My choice would be to take a train to Pisa or Bologna and use EasyJet from there. The rail trip from Firenze SMN to Pisa Aeroporto is 1H:15M, usually with one change at Pisa Centrale. As with all budget airlines, BE SURE to read the "Terms & Conditions" carefully, especially related to baggage limits. With many airlines in Europe, only ONE carry-on item is usually allowed. That doesn't mean "one plus a personal item such as a Purse or Laptop case", it means ONE ONLY of the approved size (*and they likely will verify the size). Happy travels!

You should also be aware that you probably will not be assigned a seat. They're up for grabs, which is not as bad as it sounds, since it speeds up boarding and the flights aren't very long.