Vito Nonumalo told Stuff he was in the back row of seats on the Wednesday evening flight from Wellington to Christchurch when there was "severe" turbulence early on.
"The jolts were big and sharp, but they were short," he said.
Both attendants were having trouble standing up.
He said he did not see the accident, but a flight attendant told him a female flight attendant hit her head on a cupboard.
Nonumalo told Stuff he saw the woman immediately after with her hand on the back of her head, apparently in pain.
"A guy in front of me jumped up and helped the other flight attendant get her into a recovery position, and they managed to get her into a seat."
That seat was on the aisle at the back and Nonumalo was in the seat on the other side of the aisle.
For the rest of the flight he and the passenger on the other side of the attendant tried to keep her awake.
"We were pretty worried about her."
She seemed to be going in and out of consciousness for about 30-35 minutes until the flight reached Christchurch, Nonumalo said.
After landing, paramedics came on board to assess the attendant, who was taken off the plane ahead of the passengers.
Nonumalo said he and the other two passengers who helped hoped they might be able to find out if the attendant was all right.
"The three of us would really like to have known whether she was okay," he said.
"The other two guys were absolutely fantastic in how fast and calmly they responded."
Air New Zealand said it could not provide any information.
"Thank you for your care and concern, but for privacy reasons, we are unable to comment," an airline spokesperson told Stuff.
