Prospective travellers to Iceland can choose between the following 17 airlines planning to operate at Keflavik International Airport this summer, 2013:   

Air Berlin
Air Greenland
Austrian Airlines
Avion Express (WOW Air)
Delta Air Lines
Deutsche Lufthansa
easyJet
Edelweiss Air
Germanwings
Icelandair
Niki Luftfahrt
Norwegian Air Shuttle
Primera Air
Scandinavian Airlines System
Thomas Cook Airlines
Transavia.com
Vueling Airlines
 
Keflavik International Airport has announced plans to accommodate the increased traffic resulting from the record number of airlines servicing Iceland this summer by opening a new departure gate, adding more self-service check-in kiosks and offering free Wi-Fi throughout the airport.   
 
The number of airlines operating during winter also increased from three to six since last winter. Iceland has simply never been as accessible!

Source: Keflavik International Airport and Iceland Review.