There is a risk of UK airspace closures from Sunday because of continuing volcanic activity in Iceland, according to the Department for Transport.
Disruption could last until Tuesday and could affect some of Britain's busiest airports in the South East, the Government warned.
The Department of Transport said: "Within this timeframe, different parts of UK airspace - including airspace in the South East - are likely to be closed at different times."
The prediction of closures from Sunday until Tuesday morning is based on continuing volcanic activity in Iceland and prevailing weather conditions. Transport Secretary Philip Hammond said passenger safety is the Government's top priority.
Nats, the UK's air traffic services provider, will announce any airspace restrictions if they become necessary and passengers are advised to check with their airlines before travelling to the airport.
In a bid to help air passengers Ministers also agreed that five-day ash prediction charts should be made available on the Met Office website.
Previous forecasts were only given for the following 18 hours but the Government statement stressed that the new five-day charts will be based on assumptions about future volcanic activity and will remain tentative.