RESTRICTIONS on flights in and out of the UK have been extended to 1pm on Sunday as Britain's air travel nightmare showed no signs of ending.

Cardiff and Bristol airports are among those to remain closed until 1pm tomorrow.

Air traffic control company Nats said the ash cloud caused by an erupting Icelandic volcano was still moving around and changing shape so the flight ban had to continue.

"Based on the latest information from the Met Office, Nats advises that the restrictions currently in place across UK-controlled airspace will remain in place until at least 1300 (UK time) tomorrow, Sunday 18 April," a spokesman said.

Volcanologists said the eruptions from Mount Eyjafjallajokull could continue for months.

And officials said airlines would continue to be subject to restrictions for as long as ash billows into British airspace.

Graeme Leitch, of the Met Office, said a change in the wind direction might mean flight restrictions could be lifted but there was no indication that any such change was imminent.

Forecaster Paul Knightley, of Meteo Group, the weather division of the Press Association, predicted the continued activity could herald "quite a prolonged spell of problems" in the UK, continuing until Friday.

Dr Dougal Jerram, of Durham University's Department of Earth Sciences, said: "We know when things are going to happen, what is difficult to predict or understand is how long a volcanic eruption is going to go on for. Some are relatively short-lived, but some are months long."

Airports operator BAA said flights from all its airports were suspended until 1pm on Sunday at the earliest and passengers should not go to the airport. "We appreciate the continued patience of passengers at this difficult time and will provide updates as often as possible," a spokesman said.

British Airways cancelled all long and short-haul flights in and out of the UK on Sunday, while budget carrier Ryanair has cancelled all its scheduled flights to and from the UK, Ireland, Denmark, Finland, Norway, Sweden, Belgium, Holland, northern France, northern Germany, Poland and the Baltic States until 1pm on Monday.