taxi fare from Naples historic center to Naples international airport

In Naples to catch a flight we stayed near the train station and took the bus in front of the station it costs 5 euros.
We toured the old town seeing the castle and the main square and went back to the hotel near the train station in order to walk from our hotel and catch the bus the next day.

Thanks jazz+travels. How long did the bus take, and do you have a hotel you would recommend?

I took metro (line nr 1, the same that passes Toledo) towards Garibaldi, and the same bus mentioned above (in front of the main door of the station). More or less 15 mnts (probably less) to airport. I did the same thing on arrival - bus (in front of airport), and metro towards my apartment. I heard that price for bus ticket is 4 euros if you buy it inside the airport at a quiosk, but I did't care for one euro, and bought it in the bus.

Our taxi from Grande Hotel Oriente about two blocks off Via Toledo to NAP at the end of our RS South of Italy tour was €25.
After returning our rental car to NAP the next day, we stayed at Stelle Hotel which is literally at Napoli Centrale train station. Taxi fare was €25 although they wanted to charge us the “Sunday” rate €30. After getting lost driving in Naples I just didn’t want to deal with buses.

the flat taxi fare is either 18€ or 21€ depending on which area of the historical center..

You can use Google to find the flat rate for taxis in Naples to and between locations in the city.

And in fact, you need to download the flat rate taxi fare list .PDF and print it, in case the driver tries to tell you at each bag is 2 Euros, which is not true! It's written in simple Italian, but you can use Google Translate for help.

Early May, this year, we stayed at the Dimora Delle Arti, a few blocks south of the Archaeology Museum (1/3 the way to Toledo). The taxi fare to the airport was about 18 Euros.
You need to have the correct cash.