Peter Gibbs explains how the ash cloud is moving in the UK's airspace
Many UK airports are closed until Monday morning because of volcanic ash from Iceland, with more disruption likely over coming days.
The no-fly zone will also see Heathrow, Gatwick and London City shut from 0100.
Manchester, Liverpool, East Midlands, Birmingham, Teesside, Norwich and Doncaster airports are among those closed in England.
Airports in Northern Ireland, parts of Scotland, some Scottish islands and the Isle of Man are also affected.
Travellers are urged to check with their airline.
The air traffic authority Nats said the Civil Aviation Authority had been forced to extend a no-fly zone imposed earlier on Sunday after the ash cloud had spread further south.
In England, other airports inside the no-fly zone include Humberside, Leeds Bradford, Blackpool, Sheffield, Doncaster and Carlisle.
In Wales, Caernarfon is the only airport affected.
All three Northern Ireland airports - Belfast International, George Best Belfast City Airport and City of Derry Airport - have also been shut.
In the Irish Republic, Dublin Airport is closed until at least 0900 on Monday.
Donegal, Sligo and Ireland West airports have been closed until 1200 on Monday, and Galway until 0900. Waterford Airport was due to close on Sunday evening until at least 0900 on Monday.
In Scotland, Prestwick airport, near Glasgow, said it would not "receive" any flights until 1245 on Monday. Aberdeen airport said it will close between 0100 and 0700 on Monday.
The UK no-fly zones are set out by the Civil Aviation Authority using Met Office data.
Nats said London's airports should remain clear of the no-fly zone until 0100 BST on Monday.
In a statement, it said the ash cloud would continue "to change shape and move further south to just north of Oxford during this period".
A Met Office forecaster said ash which exceeded the acceptable level for flights would "clip" London in the early hours of Monday morning, but the plume would drift away during Monday night and Tuesday.
The cloud is likely to have drifted out of UK airspace by Wednesday.
Scottish Finance Secretary John Swinney said: "Current predictions suggest the situation is likely to worsen over the next 24 hours before easing into Tuesday."
Ash from the Eyjafjallajokull volcano has caused disruption to thousands of flights since April.
Coaches were used to transport stranded passengers
A spokesman for Manchester Airport said the latest disruption to flights was not expected to reach the level which previously left thousands of passengers stranded abroad.
He said: "There is absolutely no official suggestion or prediction that the prolonged, continent-wide airspace restrictions experienced in April are about to occur again."
The Association of Train Operating Companies (Atoc) said extra services were being put on to help those affected by the flight ban.
Network Rail said engineering works would be postponed where necessary.
Eurostar said it planned to run extra trains between Paris and London on Monday as a result of the disruption to flights.
While some airports came to a standstill, activity at others increased.
Airline Jet2.com said it was mounting a "massive operation" to get passengers into and out of Newcastle Airport as it took "advantage of this last remaining open airport" in the north of England.
Dr Dougal Jerram, a volcanologist from Durham University, warned the last big eruption of Eyjafjallajokull - in the 1820s - went on for about two years, and its current eruption could last "several months".
Aviation expert David Learmount warns the ash could cause disruption for 20 years
But he said the continued eruptions would not necessarily cause more problems to air travel, as a number of factors - explosive eruptions, a concentrated plume and certain weather patterns - needed to be in place at the same time to create "the perfect storm".
Aviation expert David Learmount told the BBC the ash from the volcano could cause disruption for years.
He said: "This could go on for 20 years or more. We just don't know how long this volcano is going to erupt for.
"Technologically there's nothing we can do about this. We cannot build engines and aircraft which can fly safely through volcanic ash, it's just out of the question.
"The only thing that we can do is get better at predicting precisely where every part of the volcanic ash cloud is."
In April, airspace across Europe was shut down for five days over concerns ash could turn to molten glass in high temperatures, crippling plane engines.
Scientists and engineers have since revised the safe-to-fly threshold, but clouds of volcanic ash have continued to drift over Europe, causing airport closures, flight delays and cancellations.
In the past week, several airports in southern Europe have been forced to close and flights have been re-routed.
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