The fifth person - a male passenger in the boat that crashed on the Shotover River about 11.40am - would stay in hospital overnight as a precaution, a KJet spokeswoman said.
The company had started an internal investigation into the incident and it would work with authorities including the police, Queenstown Lakes District harbourmaster and the Transport Accident Investigation Commission, she said.
Twelve people were in the boat when it crashed and seven of them did not require more than assessment or treatment at the scene, a St John Ambulance spokeswoman said.
One of the people flown to the Queenstown Lakes District Hospital was the driver of the boat.
The driver was discharged this afternoon, the KJet spokeswoman said.
Three other patients were assessed at the Queenstown Hospital and discharged, she said.
KJet suspended operations after the incident.
The spokeswoman said the company was supporting all the passengers who were on board, their friends and family, as well as the driver.
