More than 250 flights from London's Heathrow and Gatwick Airports, including to and from India, were grounded on Thursday due to ash from Iceland's spewing volcano.
The flying ash also affected flights from Scotland with air traffic controller warning that more airliners could be disrupted as the volcano was expected to continue eruptions for the second time in less than a month.
The grounding of flights on the British Airport came as hundreds of people fled Iceland because of rising flood waters
around the volcano under the Eyjafjallajokull glacier.
Airports in the Scotish cities of Glasgow, Edinburgh, Aberdeen were closed to flights and air connections to other British cities of Newcastle, Birminghum, Manchester, Luton and Stansted were also affected.
A Heathrow Airport spokesman said 150 flights, both arrivals and departures, had been cancelled and more flights were expected to be affected as the cloud of ash moved south.
At Gatwick, 108 flights have been cancelled.
The British Airport Authority (BAA) said, "On advice from the Met Office, the National Air Traffic Service has introduced restrictions to UK airspace from this morning as a result of volcanic ash drifting across the UK from Iceland."
"These measures currently affect Aberdeen, Edinburgh and Glasgow airports which are closed but may also affect other parts of the UK later today".
"Passengers intending to fly today are asked to contact their airline for further information and should expect disruption in the coming hours".
Forecasters said the ash could take a number of days to disperse. National Air Traffic Service said, air space had been restricted as volcanic ash represented a significant safety threat to aircraft.
Iceland, a nation of 320,000 people, sits on a large volcanic hot spot in the Atlantic's mid-Oceanic ridge.