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UK Civil Aviation Regulations

These are published by the CAA on our UK Regulations pages. EU Regulations and EASA Access Guides published by EASA no longer apply in the UK. Our website and publications are being reviewed to update all references. Any references to EU law and EASA Access guides should be disregarded and where applicable the equivalent UK versions referred to instead.

Since the 2010 volcanic ash crisis, measures have been put in place to ensure that the UK, and the aviation industry worldwide, is prepared for a similar event. The following arrangements now apply in UK airspace, and across much of Europe, in case airspace is affected by volcanic ash.

Areas of ash are identified using information provided by the Met Office's Volcanic Ash Advisory Centre. They supplement this with annotated satellite information showing the likely location(s) of the ash, and forecast ash concentration charts which provide information on the concentrations of volcanic ash you are likely to encounter in that airspace, as described below.

Any UK airline wishing to operate in areas of airspace forecast to be, or aerodromes/operating sites known to be, contaminated with volcanic ask will need to complete an assessment of the safety risks related to known or forecast volcanic ash contamination as part of its management system.

Airspace contamination level Ash per m3 of air Information provided by Advice
Low Greater than 0.2 but less than or equal to 2.0 milligrams SIGMET and Volcanic Ash Advisory Centre graphics
  • Engine manufacturers suggest short periods of flight should not lead to a significant reduction in engine related flight safety margins
Medium Greater than 2.0 but less than 4.0 milligrams Volcanic ash supplementary products issued by the UK Met Office and Météo-France
  • UK airlines must have a safety case accepted by the CAA to operate*
  • Some airlines already have safety cases in place and agreed for operation
High Equal to or greater than 4.0 milligrams Volcanic ash supplementary products issued by the UK Met Office and Météo-France
  • UK airlines must have a safety case accepted by the CAA to operate*
  • Some airlines already have safety cases in place, and are allowed to operate as long as they are satisfied that no high density ash is present at the actual time of flight

* Non-UK airlines can apply to their own national regulator for similar safety cases.

The new regime maintains high levels of safety while reducing disruption. According to the European air traffic control body Eurocontrol, only 900 of the 90,000 flights due to take place in Europe during the Grimsvotn eruption (23-25 May 2011) were cancelled. Work continues to implement one common regime worldwide and the CAA is directly involved in driving this work in Europe and through the International Civil Aviation Organisation.

More information

Safety cases

Safety cases have been used to set out how they will safely deal with unusual or challenging issues for main years. They set out the measures that airlines will put in place to mitigate risks, in this case of flying through ash. They also include input from aircraft and engine manufacturers, which is important as they can advise on the levels of ash that their engines can safely cope with.

A safety case needs to show that the airline understands the hazard and its own limitations, and that it has in place robust procedures and plans to safely fly in the unusual situation. These procedures may include extra training for crews, additional maintenance inspections, and guidance for pilots as to how they shout react in certain circumstances.

Safety cases are put together by the airlines and presented to their regulator (the CAA for the UK) for acceptance.

Close Safety cases

Forecasting of ash

The Met Office uses a computer modelling system known as the NAME model to predict where ash will be present and in what density.

The model has been widely endorsed by the international meteorological community and has been tested and proven during previous eruptions and events including Chernobyl and Buncefield.

The Met Office model forecasts the presence of ash, and makes use of a range of information sources including at the source of the volcano, satellite images, test flights, weather balloons and ground based instrumentation.

Close Forecasting of ash

Effects on small light aircraft

Piston engine aircraft (typically used for recreational flying) are less affected by ash, so in some cases may still operate when commercial jet airliners are not flying.

Close Effects on small light aircraft