I wonder whether there will be extensive testing regime present when international flights resume later this year.
Initially, you may face lengthy delays at airports because some ports will require you to undergo COVID-19 testing, which may take an hour for the test to have a result, before you are allowed to board an aircraft.
You may also be required to show from a doctor a few days before departure that you don't have COVID-19 in order to obtain immigration clearance.
My guess is that international travel will be open in stages, where we will see NZ open first hopefully in June, followed by selected Asian countries with good quarantine measures such as Korea, Hong Kong, Taiwan (and potentially Singapore) open in July/August, before opening the rest of the world by the year's end.