Parts of British airspace may have to close from Sunday until Tuesday due to volcanic ash from Iceland, UK's department of transport says.
It said parts of the airspace, including the south east, where Europe's busiest airport Heathrow is located, were likely to be closed at different times.
"Due to continuing volcanic activity in Iceland and prevailing weather conditions, if the volcano continues to erupt at current levels UK airspace will be at risk of closures," the department said in a statement on Saturday.
Spewing ash from the erupting Eyjafjallajokull volcano in Iceland grounded much of European air traffic for nearly a week in mid-April.
Airlines had to cancel around 100,000 flights, stranding millions of passengers.
Since then the ash has periodically forced short-term closure of parts of airspace in countries across Europe, including Spain, Portugal, Ireland and Germany.
Philip Hammand, the British transport minister, said on Saturday that five-day rather than the previous 18-hour ash prediction charts would be made available to airlines and the public on the Met Office forecaster's website.