A look at the role of the CAA following the Eyjafjallajokull volcanic eruption in Spring 2010.
Wednesday 14 April
More forceful eruptions start emitting plumes of ash.
The CAA is informed and advice is provided to airlines.
As the extent of the ash cloud becomes clear, the CAA-led National Airspace Crisis Management Executive meets for the first time. The group continues to meet three times a day throughout the crisis.
Thursday 15 April - UK airspace affected
Early morning – the ash cloud reaches Scottish airspace making it impossible to operate using existing ICAO guidance.
In accordance with the ICAO guidance NATS announces that from midday to 6pm, it will not provide a service to commercial operators into the contaminated airspace. CAA follows this with a NOTAM (Notice to Airmen) reinforcing the decision.
Six Met Office ground-based Light Detection and Ranging Radars (LIDAR) detect ash in the atmosphere and a test aircraft is launched for airborne evaluation.
Friday 16 April
Evidence of ash presence is detected at various locations throughout UK. A small window allows Manchester Airport to open briefly.
The CAA, NATS and Met Office in contact with Eurocontrol. CAA meets Secretary of State for Transport and agrees further updates and briefings throughout the day, including afternoon meeting with airlines and airport representatives. Regular contact continues throughout the crisis.
The CAA establishes international teleconference calls, drawing together almost 100 organisations to assess whether slightly denser contamination than the current ICAO level would be safe.
Saturday 17 April
There is no positive prognosis for allowing flights to recommence due to further eruptions and settled weather patterns which keep the ash over the UK.
An aircraft operator in Penzance detects ash on airframe on landing. Similar reports from MoD in West Wales and North England.
Tests throughout the weekend tests show the continued presence of contamination.
Sunday 18 April
Further International teleconference calls take place. More data is requested by engine manufacturers on likely levels of contamination before they will agree to a new level of safe ash.
An instrumented test aircraft validates a British Airways flight to measure contamination levels and practical impact.
Monday 19 April
The CAA continues to seek agreement from aircraft engine manufacturers – overnight work in the US suggests a solution may be possible.
European Transport Ministers meet and agree a three band model for classifying ash. Eurocontrol announces that a new zoning system will take effect from 0600 on 20 April.
At the next international teleconference, data is examined from further instrumented flights which show low level contamination. But there is still no uniform agreement from engine manufacturers about changing the tolerance level.
Tuesday 20 April
A further international teleconference with the same participants takes place.
A CAA emergency Board meeting held at 17:30 agrees a way forward with 2 milligrams per cubic metre of air set as an acceptable safety limit.
Requirements are established for airlines, Air Traffic Control and aerodromes that include a range of inspections to engines and airframes between flights.
Test flights continue to monitor ash density.
The CAA briefs the Secretary of State for Transport and airlines and announces that airspace will be re-opened at 22:00.
Nine engine manufacturers go public with support for the new safety thresholds.
Airspace then remains open as normal until 3 May.
The ash plume returns to parts of UK airspace and contamination levels exceed the new safety threshold for several days. This results in airports being closed in Scotland and Northern Ireland.
From then onwards UK airspace remains open as usual.
A high concentration of ash in airspace over parts of the south west, southern and central Europe, leads to airport closures in those areas.
How we are planning for future ash events