Ryanair is again demanding that the UK adopt a new system of protection against volcanic ash, after the Icelandic eruption disrupted operations at several airports in the country.

London Heathrow and London Gatwick had been affected early today but operator BAA subsequently stated that restrictions were lifted at around 11:00 - a decision which has led Ryanair to question whether the London airports' importance resulted in their being treated more leniently.

Airlines have become increasingly sceptical about the validity of ash concentration forecasts and modelling from the London Volcanic Ash Advisory Centre, which oversees the area affected by the Icelandic eruption.

Ryanair claims the VAAC's forecasting is not only unreliable but "substantially fictitious".

"It would appear that there is one model for air safety for all other UK airports, but when it threatens the opening of Gatwick and Heathrow, these [forecasts] are simply ignored," it adds.

"Today's decision to re-open Gatwick and Heathrow airports, despite the fact that this imaginary black cloud or 'no-fly' zone is hovering right over Heathrow and Gatwick, proves that the [VAAC charting] no longer retains any credibility or confidence within the airline industry."

Ryanair is insisting that the UK adopt a system whereby airspace within a 60mi (100km) radius around a volcano is declared hazardous, but airlines are permitted to fly outside of this zone as long as ash is not visibly present. If ash is detected on the airframe after landing, the carrier follows manufacturers' guidelines.

"There cannot be one safety model for busy London airports, and a different safety model for smaller regional airports," says Ryanair chief Michael O'Leary, adding that the ash forecast charts have "no validity or credibility". He adds: "It should and must be one safety rule for all."

Source: Air Transport Intelligence news