Ash Cloud from Chilean volcano entering New Zealand Airspace

The CordónCaulle eruption began on 4 June 2011 with the initial ash plume reaching above 50,000ft. Volcanic ash particles come in a range of sizes and while the biggest will fall to the ground quickly, very small particles take a long time to settle out of the atmosphere. This eruption ejected these small particles very high into the atmosphere, where strong winds have carried them great distances to the east.

There is potential for ongoing ash plumes to arrive over southern parts of New Zealand as early as Saturday evening, spreading northwards through the remainder of the weekend. The plumes are expected to be at cruising levels for both jet and turboprop aircraft (20,000 - 35,000 ft), but at the moment not below 20,000ft. Given that the volcanic activity is continuing, it is expected that New Zealand airspace may be affected by these plumes for at least a week.

New Zealand has a mature Volcanic Ash Advisory System with inputs from MetService, the Institute of Geological and Nuclear Sciences, the Airways Corporation, and aircraft operators that ensures that civil aviation aircraft operations can be safely carried out near volcanic ash. The CAA is also communicating with the Australian Civil Aviation Safety Authority (CASA), to ensure both countries have the latest information available.

MetService, on behalf of the Civil Aviation Authority, operates the Wellington Volcanic Ash Advisory Centre (VAAC) as part of the International Civil Aviation Organisation's International Airways Volcano Watch system. MetService will track the volcanic ash plumes and provide warnings to the aviation community here and over the wider VAAC area (roughly Equator to the Pole and mid-Tasman to just west of South America).

At this stage the forecast trajectory of the volcanic ash plumes may initially have an effect on air traffic routes over the South Island, the Christchurch to Australia routes, and the great circle routes between Australia and New Zealand and South America. The situation is being closely monitored and other air traffic routes may be affected as volcanic ash forecasts are updated. Based upon information provided by MetService, airlines will adjust their flight routes and altitudes to remain clear of the ash clouds. Safety of the air operations is the primary goal, and flight disruptions will be minimised as much as possible consistent with this objective.