Cagliari is the main city in southern Sardinia. It can be easily reached by plane from Italy main land, e.g. via Milan or Rome, and from abroad, e.g. from Amsterdam, London, Düsseldorf, Göteborg, Barcelona, Madrid. Here is a map of all the destinations. The direct international routes are mainly served by low-cost companies such as Ryanair and Easyjet.
The city airport is Cagliari Elmas, only 10 minutes from the city by public transport. From the Elmas airport you can either take a train to the Cagliari train station or a taxi.
The airport train station is about 5 minutes from the arrival hall; follow the "Train" signs to the left. The rail service starts at about 5AM and ends after 9PM with 20 mins. average frequency. The journey to and from downtown takes 5-7 mins, single fare is 1.30 euro. Tickets are sold by Trenitalia at the vending machines (located both in the arrivals area of the terminal and inside the train station), online, and by official ticket counters and authorized dealers.
Train timetables can be found online but are, sometimes, unreliable. It's hence best if you simply look at the departure panel located in the arrival hall and check when the next train is due. Cagliari train station is located in piazza Matteotti, in the city centre.
Taxis can also be found outside the arrival hall. A ride to the city centre costs about 20-25 euros. Car rental companies are located in a dedicated area in front of the terminal.
More information, visit the airport website here.
Alternatively, if you don't want to fly, you can take a ferry boat (from Civitavecchia, Napoli, Palermo, or Trapani) to Cagliari. The harbour is also in the city centre, close to piazza Matteotti.
