Today many airports in the UK are being affected by a cloud of volcanic ash drifting from Iceland. So far Edinburgh, Glasgow and Aberdeen airports have been shut. Manchester are still running some flights but Birmingham has already closed. Heathrow and Gatwick have yet to be effected but Gatwick believe they will not need to close down. 
The volcanic eruption occurred several weeks ago but yesterday saw a particularly violent eruption that sent the cloud of ash over the UK. The cloud is projected to move further south during the day.