The National Air Traffic Control Service (Nats) said Met Office forecasts showed the ash cloud progressively covering the whole of the UK after 1900 BST. A further update is expected at about 2100 BST.

Nats head of safety Paul Haskins said: "It's a very dynamic situation at the moment. There may be opportunities for one or two flights this afternoon.

"Looking at the Met Office forecast we know from about seven o'clock onwards this evening that the ash cloud will again envelop UK air space and the restrictions will take effect."

Prof Brian Golding, head of forecasting research at the Met Office, said it was likely the volcanic cloud would remain over the UK for several days.

"We need a change of wind direction that stays changed for several days and there is no sign of that in the immediate future," he added.