Loganair is cancelling almost all its flights in Scotland on Thursday because of expected disruption caused by the ash cloud. Only inter-island routes in Orkney are unaffected.
A Loganair spokesman said Met Office forecasts indicated that a high density of ash would be present in large parts of Scottish airspace throughout Tuesday, clearing into Wednesday morning.
The UK's air traffic control service, Nats, said volcanic ash was forecast to affect parts of Scotland between 1800 BST and midnight on Monday.
Services may be affected from Barra, Benbecula and Tiree.
BBC News - UK flight disruption cannot be ruled out - CAA