Airports in Northern Ireland, Scotland and northern England are currently being affected by a high-density volcanic ash cloud, although London airports remain open at present.
A statement on the NATs website (released at 1030 BST today, Sunday May 16) advises:
"The CAA's no-fly zone required by the high density volcanic ash cloud will not affect London airports for the period 1300-1900 (local time) today.
"The no-fly zone for this period has moved east to a line stretching from Prestwick on the west coast to Humberside on the east coast and south to a line just north of Birmingham.
"Airports which fall within the no-fly zone include all those in Northern Ireland, Ronaldsway, Prestwick, Carlisle, Manchester, Liverpool, Doncaster, Humberside, Leeds Bradford and East Midlands and some Scottish island airports including Campbeltown, Islay and Barra.
"There are currently no other restrictions within UK airspace. Information about Irish airspace can be found at on the IAA website.
"We are working closely with the Met Office and with the CAA, which agrees no-fly zones based on Met Office data, and will issue any further notice on this website as necessary."
Current forecasts suggest the ash cloud may extend further southwards on Monday and Tuesday, potentially affecting London airports early next week.
For more information visit nats.co.uk.