One of the workhorses on the top dressing fleet will have go back to the maintenance hanger for vital repairs.
A double fatal crash has prompted the Civil Aviation Authority to order owners of Fletcher aircraft to fit new vertical fins.
CAA engineers started investigating Fletcher FU 24 series aircraft after one model crashed near Whangarei in 2005, killing both top-dressing crew members.
An accident report revealed the pilot most likely lost control of the plane when a weak fin failed and broke in mid-flight.
Now, the aviation regulator says top-dressing firms should fit new fins that can take more stress.
One of the biggest aerial spraying firms is Super Air.
Manager Graeme Martin says a rough estimate to do the job will be $20,000 for each plane.
According to CAA records, there have been eight fin failures on the Fletcher FU 24 series aircraft since 1973.
Owners have until October 2010 to fit the new fins.