Air passengers face the return of flight chaos as the skies over many parts of Scotland, Northern Ireland and Ireland closed for business once more.
Hundreds of flights to and from airports are to be suspended after emissions from the Icelandic volcano Eyjafjallajokull in the atmosphere increased, and there are fears airports in Wales and the North West of England could be hit later in the day.
A no fly zone will be imposed over parts of Scotland and Northern Ireland from 7am amid safety fears over concentrations of ash in the atmosphere.
The Civil Aviation Authority (CAA) said no-flight restrictions will be introduced from 7am to 7pm for Glasgow, Prestwick and Campbeltown in mainland Scotland and Stornoway, Benbecula, Tiree, Islay and Barra in the Hebrides. Inverness airport will be shut from 7am to 1pm.
No-flight restrictions will also be introduced from 7am to 7pm for Derry and from 1pm to 7pm for Belfast International and Belfast City.
In the Republic of Ireland, flights are suspended until further notice at Donegal from 8am, Sligo from 9am and Dublin and Knock from 11am. Restrictions are also likely to be imposed on Cork, Waterford and Kerry at 2pm, the Irish Aviation Authority said.
It is forecast that the ash plume will exceed the safe level agreed by aviation manufacturers.
The return of the ash cloud caused the closure of airspace in the Republic of Ireland and in Northern Ireland until 1pm on Tuesday. Hundreds of flights had to be cancelled, with services in the Hebrides and parts of northern mainland Scotland also affected.
Flights from continental Europe were not affected by the ash cloud. Transatlantic services passing over Ireland and Northern Ireland were also unaffected.
As travellers struggled to cope with the disruption, the Association of British Insurers said insurance companies were likely to have to pay out around £62 million to those affected by last month's ash-cloud chaos.