MBIE said rooms were occupied for a minimum of 14 days and additional time was needed for cleaning and maintenance. This meant this full 14 day period was considered as opposed to room availability on any single day.
Rooms that were vacant on one day might be needed for an incoming flight the next day, so were not actually available.
For various reasons, such as international travel volatility, not all people who have vouchers would use them and MBIE said vouchers were released as they became available.
In total, 93,898 people had been through MIQ facilities since March 26, 2020.
No plans for more facilities; MIQ working through flight changes
A MIQ spokesperson says managing the country's 32 managed isolation facilities, and the almost 5800 people staying in them, was a complex logistical exercise.
There were facilities in Auckland, Hamilton, Rotorua, Wellington and Christchurch, and the spokesperson said there were no plans to establish MIQ facilities in any other locations.
"A key constraint on adding new facilities is the essential workforce who care for returnees. We need nurses, defence personnel and police to run these facilities, and this is a limited workforce.
"In addition to workforce supply issues, there are a number of complex issues that need to be considered when operating in a Level 4 environment. This includes the limited number of suitable facilities that are in locations where there is also a suitable hospital facility and proximity to appropriate transport hubs."
The spokesperson said MIQ has a strong relationship with airlines flying to New Zealand and it was communicating with them about the increasing demand for vouchers and space in managed isolation facilities.
Due to the international upheaval to air travel caused by Covid-19, flight data can be very changeable but the MIQ spokesperson said it was in constant contact with airline carriers.
"Airlines advise us of their confirmed flight schedules, which we then load into the managed isolation allocation system," the spokesperson said.
"We are limited to how far out we can upload information from airlines, and confirmations of flights more than two to three months ahead are very unreliable as they are highly susceptible to change.
"This will impact on people booking when they are unable to find their flight details in the managed isolation allocation system, because the flight has not been registered or the time has been altered."
The spokesperson said MIQ encouraged people to contact their airline to confirm their flights in these situations and this was mentioned on the Managed Isolation Allocation System website when it went live on 5 October.
They said most airfares were selling tickets that are fully flexi.
- RNZ