British aviation regulators said airspace over Scotland and Northern Ireland will close as from 7 a.m. (0600 GMT) today due to dangers posed by ash from an Icelandic volcano.
They also warned the ash cloud may float further south and close airports in other parts of Britain.
"Forecasts show that levels of ash in the atmosphere over Scotland and Northern Ireland will exceed the concentrations that engine manufacturers have agreed are safe for operations," said Britain's Civil Aviation Authority (CAA) in a statement yesterday.
"Unfortunately, this means that the CAA anticipates all Scottish and Northern Ireland airports will be closed from 7 a.m. local time tomorrow."
The CAA gave no indication when the airspace might reopen.
"The UK Met Office (weather forecasting service) has informed the CAA that ash over UK airspace has increased in density as ash emissions from the Icelandic volcano... have become stronger," said the statement.