Human error, exacerbated by social media threats, meant an emergency medical flight couldn't land at Kāpiti Coast Airport late at night.
The airport was temporarily closed on Sunday, December 13 after a security risk stemming from social media threats.
But aerodrome flight information service (AFIS) staff didn't switch the tower controlled runway lighting to pilot activated control before they vacated the airport.
"There were people who made serious threats online towards Airways and Kāpiti Coast Airport staff because they don't agree with the rolling closures at Kāpiti Coast Airport due to Airways' inability to provide a full AFIS roster at the moment," airport spokeswoman Dani Simpson said.
"The behaviour of those people was completely unacceptable and they do need to understand the seriousness of their actions, which directly contributed to a situation where Airways' staff member had to leave the tower under urgency.
"Given the threat, Airways made the decision to remove their staff member from the tower at the end of their shift and the airport was temporarily closed while the threat was investigated."
Late that night, an Air Wanganui flight transporting a Nelson mother so she could be with her seriously ill baby, who was being treated at Wellington Hospital, tried to land at Kāpiti Coast Airport four times without success because the runway lights couldn't be activated.
The plane, which couldn't land at Wellington Airport because of scheduled maintenance, flew to Palmerston North Airport, before the woman was helicoptered to Wellington Hospital but it was believed her baby died before she got there.
After police investigated the social media threats, and decided not to take the matter further, Kāpiti Coast Airport reopened the next day.
"With regards to the runway lighting outage, from a safety management procedures perspective, we have logged this internally as an incident requiring further investigation," Simpson said.
"We have also lodged a 005 Occurrence report with CAA – that report enables CAA to look at incidents to evaluate whether further follow up action is required."
An Airways spokesperson said the incident had been reported to CAA, Airways was reviewing its processes "for leaving a tower under urgency" and it was "providing appropriate support to our staff who were at work when the security threat was received".
Air Wanganui was also conducting an investigation, chief executive Dean Martin confirmed.
Tim Costley, spokesman for Save Kāpiti Airport, said the medical flight incident demonstrated "how critical our airport is for the resilience and wellbeing of our region and the wider community".
"Wellington Hospital relies on Kāpiti Coast Airport - it is regularly used by life flights, and aeromedical flights, and when planes can't land in Kāpiti, they have to divert to Palmerston North which is too far away from Wellington to make a difference in the golden hour."
The incident also came at a time when rolling closures were introduced at Kāpiti Coast Airport, in line with the airport's exposition, during parts of the day, until at least February 1, because of an AFIS staffing shortage at the airport.
Costley described the rolling closures as "madness".
"The airport has always been used outside AFIS hours by day and night, like these nighttime medical flights, even though there are no AFIS staff.
"If the owners are happy for these night time flights to occur with no AFIS staff, why can't pilots also fly by day during the short windows when AFIS staff are not present?
"Every pilot will tell you that flying by day is much safer than flying by night."
The Save Kāpiti Airport group was formed after fears NZPropCo, who own Kāpiti Coast Airport, will close the airport.
Templeton Group, which is in charge of the airport on behalf of NZPropCo, are looking at all the options for the airport's future viability.