Air New Zealand, with an office at Rarotonga Airport, has direct service to Rarotonga from Auckland (once or twice a day) and Los Angeles (weekly). Air New Zealand services into Rarotonga are heavily booked, so reserve your inward and outward flights as far ahead as possible. If you try to change your outbound flight after arrival you could be put on standby.
The Australian no-frills carrier Virgin Australia has two flights a week from Auckland to Rarotonga. Food, drink, and movies all cost extra on Virgin Australia's cramped planes, and their low-priced tickets carry restrictions and penalties you should consider before booking.
In 2007 Air New Zealand canceled its flights to Rarotonga from Fiji and Tahiti. To reach the Cook Islands from Fiji, Samoa, or Tonga, you must travel via New Zealand. From Tahiti, Air Tahiti and Air Rarotonga launched a joint Papeete-Rarotonga service which operates weekly.
Check in for your outgoing international flight at least one hour before the scheduled departure time, as the airlines are short of staff: If everyone is needed to attend to a flight arrival, they may simply close the check-in counter and you'll be out of luck.