The Civil Aviation Authority (CAA) has announced the introduction of a new Time Limited Zone (TLZ) which will allow flights to take place though denser ash cloud than previously permitted.

Following discussions with airlines, regulators, and aircraft and engine manufacturers the new Time Limited Zone, which effectively doubles the amount of permissible ash grammes per cubic metre of air, will reduce the need for airspace closures caused by volcanic ash.

New procedures and the introduction of the zone will take place from midday today, 18 May 2010.

To operate in the new zone airlines need to present the CAA with a safety case that includes the agreement of their aircraft and engine manufacturers. UK airline Flybe is the first to achieve this and will therefore be able to use the new zone from midday.

Announcing the change Andrew Haines, Civil Aviation Authority Chief Executive, said: “I’m pleased that the huge efforts we’re all making across aviation to keep flying safe whilst minimising the disruption from the volcano have resulted in further progress. Unprecedented situations require new measures and the challenge faced should not be underestimated. Firstly because the standard default procedure for aircraft that encounter ash, to avoid it completely, doesn’t work in our congested airspace. Secondly, the world’s top scientists tell us that we must not simply assume the effects of this volcano will be the same as others elsewhere. Its proximity to the UK, the length of time it is continuously erupting and the weather patterns are all exceptional features.

“The answer can only come, therefore, from aircraft and engine manufacturers establishing what level of ash their products can safely tolerate. At an international aviation conference we held last Thursday, attended by all the leading airline operators this approach was welcomed and supported. The manufacturers are co-operating fully and urgently in this task and the new zone is an excellent example of how the industry should be working to move the issue forward and I commend Flybe for its work.”

The introduction of the Time Limited Zone is based on measurements collected from test flights through the current ash cloud over the past month, as well as on data and evidence compiled and analysed from previous volcanic ash incidents combined with additional analysis from manufacturers.