Airways open at last

Eurocontrol map of ash plume at 1830 on April 20.
Eurocontrol map of ash plume at 1830 on April 20.

April 21: After six days of closed airspace, the UK Civil Aviation Authority (CAA) has issued new guidance on the use of the Anglo Irish Functional Airspace Block (FAB) after talks with the Irish Aviation Authority (IAA).
Airspace restrictions over the UK were lifted at 2200 BST yesterday but some ‘no fly zones’, where concentrations of ash are considered at levels unsafe for flights, could be imposed at any time if conditions deteriorate. “Making sure that air travellers can fly safely is the CAA’s overriding priority”, it said in a press release.
In reality the ‘zero tolerance’ international agreement to flying in areas where ash may be present has been relaxed. The CAA says “Current international procedures recommend avoiding volcano ash at all times. In this case owing to the magnitude of the ash cloud, its position over Europe and the static weather conditions most of the EU airspace had to close and aircraft could not be physically routed around the problem area as there was no space to do so. We had to ensure, in a situation without precedent, that decisions made were based on a thorough gathering of data and analysis by experts. This evidence based approach helped to validate a new standard that is now being adopted across Europe.”
Tolerance levels for ash have been agreed by industry and the regulators, enabling much of the airspace to be reopened around the thickest plume of the volcanic eruption in the Eyjafjallajoekull area of Iceland. The CAA stresses that the levels are “conservative”, allowing a “significant buffer on top of the level the experts feel may pose a risk”.
UK air traffic control services provider NATS says that flights have resumed in the UK with the exception of an area over the north west of Scotland, which continues to be affected by a dense concentration of volcanic ash. Eurocontrol says that most of Europe is now unrestricted, with the exception of parts of Scandinavia.