Pilots of small aircraft say they are getting inaccurate weather reports for the West Coast.
Automatic weather stations are replacing human observers at small aerodromes.
Pilots have told Radio New Zealand they are let down when it comes to reading visibility and the height of cloud - and how much is about.
They say the system is good at gauging the temperature and the direction and speed of wind.
There is no issue for commercial airliners, or their passengers, as they are watched by air traffic controller radar.
MetService says the new system is accurate. Before it was installed, the West Coast was covered by one manual observation per day from Westport and around nine from Hokitika.
Pilots can now obtain 48 observations a day.