Final answer:
Air New Zealand should report unearned service revenue of $400 on its income statement.
Step-by-step explanation:
Air New Zealand should report Unearned service revenue of $400 on its income statement after two trips have been used up.
When the customer prepays $600 for the package holiday, it is considered unearned revenue because Air New Zealand has not yet provided the service. As the trips are taken, the company recognizes the revenue for each trip that is completed. Therefore, after two trips have been used, $200 worth of revenue has been earned (2 trips x $100). The remaining $400 ($600 - $200) is still unearned and should be reported as such on the income statement.