Prime Minister Jacinda Ardern has defended Defence Minister Ron Mark's use of Royal New Zealand Air Force aircraft for transport, saying she's been assured the trips were work-related and appropriate.

National's defence spokesman Mark Mitchell this week said official information showed Air Force NH-90 helicopters and a B200 King Air aircraft have repeatedly been diverted to Mr Mark's hometown, apparently to ferry him to events around the country.

Responding, Mr Mark issued details of seven flights he had taken since becoming defence minister and said none were for personal use.

On Friday, Ms Ardern backed that up.

"For me, the question is: are they work-related? They were," she told media at Polyfest in Auckland.

"If I ever saw that being used for personal use that would be totally inappropriate."

She said while the government had to be mindful of perception, she had spoken to Mr Mark about the matter and was confident the aircraft use was above board.

According to information released by Mr Mark on Thursday, three of the flights were to or from Masterton.

He said he lived in Carterton, not Masterton, and all the flights involved official engagements. One was also a regularly scheduled flight which would have departed with or without him.

"On a number of these flights I have been accompanied by NZDF officials, MPs from other parties, and/or media representatives," he said.

"On several occasions, I have declined NZDF's offer of transport."