Every year only around 2% of scheduled flights are cancelled at Wellington Airport. If a flight is cancelled, airlines will generally add additional services or switch flights to clear any backlog. An airline may decide to cancel flights due to weather events like fog, low cloud or severe wind.
Each airline has their own guidelines in terms of whether they will operate in changing weather conditions.
At Wellington Airport our automatic weather station feeds continuous information to the New Zealand Met Service and to our control tower. The Airways Control Tower also makes weather observations every hour and report these to the New Zealand Met Service. Weather conditions are regularly transmitted over radio frequency to pilots and are updated every time the conditions exceed certain parameters.
If an airline decides to cancel flights, the airport terminal will generally still remain open during our regular operational hours. Runway closures are rare and would only happen if the runway or navigational systems are impacted in events like snow or for runway inspection after a major earthquake.