The files include reports of UFO sightings from 1979 to 1984 and references to the Kaikoura sighting of December 1978.
The files are held by Archives New Zealand and were to have been made public this month, but the Defence Force is removing personal information from them to comply with the Privacy Act.
"At the moment we are working on making copies of these files, minus the personal information," a Defence Force spokeswoman said. "Once this work is completed, we are hoping to be able to release a copy of all the UFO files, including some ahead of their release time, within the year."
Lights were seen in the sky over Kaikoura in December 1978 and were filmed by an Australian news crew. Aircraft tracked the lights, which were also seen on radar.
A man who worked for the Transport Ministry's civil aviation division when the Kaikoura lights were seen said he would like to see the government files.
The man, who wanted to remain anonymous, said he was working at Christchurch International Airport at the time. He saw United States Air Force planes with unusual call signs touring the area and believes the full story about the lights has not been disclosed.
"For the US Air Force to come all that way and spend three days here, there must have been something going on," he said.
The director of research group UFOCUS NZ, Suzanne Hansen, said she was frustrated by the delayed release but understood the privacy reasons.
"We have been in discussion with the New Zealand Defence Force for many years ... It is frustrating from a research perspective because we would like to collate these sightings with international research. Rate this posting: