How To Get There
Barcelona is your airport to get to Sitges. Check BCN airport site to see which airlines fly to Barcelona from your nearest airport: http://www.barcelona-airport.com/eng/airlines.htm
From Barcelona airport you can get to Sitges either by bus if you are landing at Terminal T1 or by train if you are landing at Terminal T2. Both rides are about 30 minutes long. You can find more info in the By Bus and in the By Train section of this page.
Girona is another relatively close airport located 130Km away from Sitges. Check this link to see which airlines fly to Girona: http://www.girona-airport.net/ From Girona airport you can rent a car or take a direct bus to Barcelona Estacion del Nord. From Barcelona you can then take a train to Sitges departing from Estacion de Francia. The distance between these two stations is 1.5Km so you can either walk or take a taxi.